feat(acl): implement OpenZaak default-fill + ZGW gateway (refs #5)

AclService.OpenZaakAsync builds a ZaakRequest from the configured defaults
(bronorganisatie, verantwoordelijkeOrganisatie, vertrouwelijkheidaanduiding,
zaaktype) plus today's date from the clock, and delegates to the gateway.
OpenZaakGateway POSTs the zaak to /zaken/api/v1/zaken with a ZGW Bearer JWT
and the CRS headers, returning the created zaak URL. Tests pass (green).

Add a root register-referentie.slnx (bff + acl) and point `make ci` at it so
the gate covers every .NET service.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Makefile

@@ -5,7 +5,7 @@
 # `make ci` locally runs exactly what the pipeline runs — no drift. Until a
 # self-hosted runner is registered, `make ci` is the gate (see docs/runbooks/ci.md).
 
-SLN        := services/bff/Bff.slnx
+SLN        := register-referentie.slnx
 COMPOSE    := infra/docker-compose.yml
 HEALTH_URL := http://localhost:8080/health
 OZ_COMPOSE  := infra/openzaak/docker-compose.yml

docs/architecture/adr-0003-default-fill.md

@@ -0,0 +1,44 @@
+# ADR-0003: ACL default-fill strategy
+
+- **Status:** Accepted
+- **Date:** 2026-06-04
+- **Deciders:** Respellion engineering
+- **Relates to:** S-04 (#5); builds on ADR-0001 (loose coupling)
+
+## Context
+
+The ACL is the only code that talks to ZGW APIs (ADR-0001 / CLAUDE.md §8.1). When the
+domain asks it to "open a zaak", the domain payload is intentionally free of ZGW
+specifics — it carries domain facts (e.g. the registrant's BSN), not OpenZaak fields. But
+OpenZaak's `POST /zaken` requires ZGW-mandatory fields: `bronorganisatie`,
+`verantwoordelijkeOrganisatie`, `startdatum`, `vertrouwelijkheidaanduiding`, and a
+`zaaktype` URL. Something has to supply those, and it must not leak into the domain.
+
+## Decision
+
+**The ACL default-fills the ZGW-mandatory zaak fields; the domain never sees them.**
+
+- `bronorganisatie`, `verantwoordelijkeOrganisatie`, `vertrouwelijkheidaanduiding`, and the
+  `zaaktype` URL come from **ACL configuration** (`AclDefaults` options) — not hardcoded,
+  not from the domain. This keeps them operationally manageable (the beheer portal will
+  edit them in S-15) and environment-specific (the seeded BIG zaaktype URL differs per env).
+- `startdatum` is derived from an injected **clock** (today's date), so it is
+  deterministic in tests.
+- The mapping from domain payload → ZGW `ZaakRequest` lives entirely inside the ACL
+  (`Application` builds the request from payload + defaults; `Infrastructure` serialises and
+  POSTs it). No other service constructs ZGW payloads or URLs.
+
+## Consequences
+
+- **Positive:** the domain stays ZGW-agnostic; ZGW knowledge is in one named place; defaults
+  are config (testable, env-specific, later editable via the beheer portal).
+- **Cost:** the ACL must be configured per environment (the seeded zaaktype URL, the
+  organisation RSINs). Missing/invalid config fails fast at the ACL boundary.
+- **Follow-ups:** mapping the BSN onto the zaak (eigenschap/rol), status transitions, and
+  documents are explicitly out of scope for S-04 and get their own slices.
+
+## Alternatives considered
+
+- **Defaults in the domain payload** — rejected: leaks ZGW concerns into the domain,
+  violating ADR-0001.
+- **Hardcoded defaults in code** — rejected: not env-specific, not operationally editable.

register-referentie.slnx

@@ -0,0 +1,13 @@
+<Solution>
+  <Folder Name="/services/" />
+  <Folder Name="/services/acl/">
+    <Project Path="services/acl/Acl.Api/Acl.Api.csproj" />
+    <Project Path="services/acl/Acl.Application/Acl.Application.csproj" />
+    <Project Path="services/acl/Acl.Infrastructure/Acl.Infrastructure.csproj" />
+    <Project Path="services/acl/Acl.Tests/Acl.Tests.csproj" />
+  </Folder>
+  <Folder Name="/services/bff/">
+    <Project Path="services/bff/Bff.Api/Bff.Api.csproj" />
+    <Project Path="services/bff/Bff.Tests/Bff.Tests.csproj" />
+  </Folder>
+</Solution>

services/acl/Acl.Api/Acl.Api.csproj

@@ -0,0 +1,14 @@
+<Project Sdk="Microsoft.NET.Sdk.Web">
+
+  <ItemGroup>
+    <ProjectReference Include="..\Acl.Application\Acl.Application.csproj" />
+    <ProjectReference Include="..\Acl.Infrastructure\Acl.Infrastructure.csproj" />
+  </ItemGroup>
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+
+</Project>

services/acl/Acl.Api/Program.cs

@@ -0,0 +1,31 @@
+using Acl.Application;
+using Acl.Infrastructure;
+
+var builder = WebApplication.CreateBuilder(args);
+
+builder.Services.AddSingleton<IClock, SystemClock>();
+builder.Services.AddSingleton(sp => sp.GetRequiredService<IConfiguration>()
+    .GetSection("Acl:Defaults").Get<AclDefaults>()
+    ?? throw new InvalidOperationException("Missing configuration section 'Acl:Defaults'"));
+builder.Services.AddSingleton(sp => sp.GetRequiredService<IConfiguration>()
+    .GetSection("Acl:OpenZaak").Get<OpenZaakOptions>()
+    ?? throw new InvalidOperationException("Missing configuration section 'Acl:OpenZaak'"));
+builder.Services.AddHttpClient<IZaakGateway, OpenZaakGateway>();
+builder.Services.AddScoped<AclService>();
+
+var app = builder.Build();
+
+app.MapGet("/health", () => "Healthy");
+
+// The ACL's single operation, exposed as a service endpoint.
+app.MapPost("/zaken", async (OpenZaakRequest body, AclService acl, CancellationToken ct) =>
+{
+    var zaakUrl = await acl.OpenZaakAsync(new DomainRegistration(body.Bsn), ct);
+    return Results.Ok(new { zaakUrl = zaakUrl.ToString() });
+});
+
+app.Run();
+
+public sealed record OpenZaakRequest(string Bsn);
+
+public partial class Program;

services/acl/Acl.Api/Properties/launchSettings.json

@@ -0,0 +1,23 @@
+{
+  "$schema": "https://json.schemastore.org/launchsettings.json",
+  "profiles": {
+    "http": {
+      "commandName": "Project",
+      "dotnetRunMessages": true,
+      "launchBrowser": true,
+      "applicationUrl": "http://localhost:5041",
+      "environmentVariables": {
+        "ASPNETCORE_ENVIRONMENT": "Development"
+      }
+    },
+    "https": {
+      "commandName": "Project",
+      "dotnetRunMessages": true,
+      "launchBrowser": true,
+      "applicationUrl": "https://localhost:7260;http://localhost:5041",
+      "environmentVariables": {
+        "ASPNETCORE_ENVIRONMENT": "Development"
+      }
+    }
+  }
+}

services/acl/Acl.Api/appsettings.Development.json

@@ -0,0 +1,8 @@
+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  }
+}

services/acl/Acl.Api/appsettings.json

@@ -0,0 +1,9 @@
+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  },
+  "AllowedHosts": "*"
+}

services/acl/Acl.Application/Acl.Application.csproj

@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

services/acl/Acl.Application/AclDefaults.cs

@@ -0,0 +1,10 @@
+namespace Acl.Application;
+
+/// <summary>Configured ZGW defaults the ACL fills in (ADR-0003).</summary>
+public sealed class AclDefaults
+{
+    public required string Bronorganisatie { get; init; }
+    public required string VerantwoordelijkeOrganisatie { get; init; }
+    public required string Vertrouwelijkheidaanduiding { get; init; }
+    public required Uri ZaaktypeUrl { get; init; }
+}

services/acl/Acl.Application/AclService.cs

@@ -0,0 +1,20 @@
+namespace Acl.Application;
+
+/// <summary>The ACL's single operation: open a zaak from a domain payload,
+/// default-filling the ZGW-mandatory fields (ADR-0003).</summary>
+public sealed class AclService(IZaakGateway gateway, AclDefaults defaults, IClock clock)
+{
+    public Task<Uri> OpenZaakAsync(DomainRegistration registration, CancellationToken ct = default)
+    {
+        ArgumentNullException.ThrowIfNull(registration);
+
+        var request = new ZaakRequest(
+            defaults.Bronorganisatie,
+            defaults.VerantwoordelijkeOrganisatie,
+            defaults.Vertrouwelijkheidaanduiding,
+            defaults.ZaaktypeUrl,
+            clock.Today);
+
+        return gateway.OpenZaakAsync(request, ct);
+    }
+}

services/acl/Acl.Application/DomainRegistration.cs

@@ -0,0 +1,4 @@
+namespace Acl.Application;
+
+/// <summary>Domain-language payload handed to the ACL. No ZGW concepts here.</summary>
+public sealed record DomainRegistration(string Bsn);

services/acl/Acl.Application/IClock.cs

@@ -0,0 +1,7 @@
+namespace Acl.Application;
+
+/// <summary>Abstracts "today" so startdatum default-fill is deterministic in tests.</summary>
+public interface IClock
+{
+    DateOnly Today { get; }
+}

services/acl/Acl.Application/IZaakGateway.cs

@@ -0,0 +1,8 @@
+namespace Acl.Application;
+
+/// <summary>Port to the ZGW Zaken API. Implemented in Infrastructure — the only
+/// code that talks to OpenZaak (ADR-0001).</summary>
+public interface IZaakGateway
+{
+    Task<Uri> OpenZaakAsync(ZaakRequest request, CancellationToken ct = default);
+}

services/acl/Acl.Application/ZaakRequest.cs

@@ -0,0 +1,9 @@
+namespace Acl.Application;
+
+/// <summary>The fully default-filled zaak the gateway will create in OpenZaak.</summary>
+public sealed record ZaakRequest(
+    string Bronorganisatie,
+    string VerantwoordelijkeOrganisatie,
+    string Vertrouwelijkheidaanduiding,
+    Uri Zaaktype,
+    DateOnly Startdatum);

services/acl/Acl.Infrastructure/Acl.Infrastructure.csproj

@@ -0,0 +1,13 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <ItemGroup>
+    <ProjectReference Include="..\Acl.Application\Acl.Application.csproj" />
+  </ItemGroup>
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

services/acl/Acl.Infrastructure/OpenZaakGateway.cs

@@ -0,0 +1,48 @@
+using System.Net.Http.Headers;
+using System.Net.Http.Json;
+using System.Text.Json.Serialization;
+using Acl.Application;
+
+namespace Acl.Infrastructure;
+
+/// <summary>The only code that talks to OpenZaak's Zaken API (ADR-0001).</summary>
+public sealed class OpenZaakGateway(HttpClient http, OpenZaakOptions options) : IZaakGateway
+{
+    public async Task<Uri> OpenZaakAsync(ZaakRequest request, CancellationToken ct = default)
+    {
+        ArgumentNullException.ThrowIfNull(request);
+
+        using var message = new HttpRequestMessage(
+            HttpMethod.Post, new Uri(options.BaseUrl, "/zaken/api/v1/zaken"))
+        {
+            Content = JsonContent.Create(new ZaakDto(
+                request.Bronorganisatie,
+                request.Zaaktype.ToString(),
+                request.VerantwoordelijkeOrganisatie,
+                request.Startdatum.ToString("yyyy-MM-dd"),
+                request.Vertrouwelijkheidaanduiding)),
+        };
+        message.Headers.Authorization =
+            new AuthenticationHeaderValue("Bearer", ZgwToken.Mint(options.ClientId, options.Secret));
+        // ZRC is a geo API; it requires the CRS headers.
+        message.Headers.Add("Accept-Crs", "EPSG:4326");
+        message.Content.Headers.Add("Content-Crs", "EPSG:4326");
+
+        using var response = await http.SendAsync(message, ct);
+        response.EnsureSuccessStatusCode();
+
+        var created = await response.Content.ReadFromJsonAsync<ZaakCreatedDto>(ct)
+            ?? throw new InvalidOperationException("OpenZaak returned an empty zaak response");
+        return new Uri(created.Url);
+    }
+
+    private sealed record ZaakDto(
+        [property: JsonPropertyName("bronorganisatie")] string Bronorganisatie,
+        [property: JsonPropertyName("zaaktype")] string Zaaktype,
+        [property: JsonPropertyName("verantwoordelijkeOrganisatie")] string VerantwoordelijkeOrganisatie,
+        [property: JsonPropertyName("startdatum")] string Startdatum,
+        [property: JsonPropertyName("vertrouwelijkheidaanduiding")] string Vertrouwelijkheidaanduiding);
+
+    private sealed record ZaakCreatedDto(
+        [property: JsonPropertyName("url")] string Url);
+}

services/acl/Acl.Infrastructure/OpenZaakOptions.cs

@@ -0,0 +1,9 @@
+namespace Acl.Infrastructure;
+
+/// <summary>Connection + credential config for OpenZaak's ZGW APIs.</summary>
+public sealed class OpenZaakOptions
+{
+    public required Uri BaseUrl { get; init; }
+    public required string ClientId { get; init; }
+    public required string Secret { get; init; }
+}

services/acl/Acl.Infrastructure/SystemClock.cs

@@ -0,0 +1,8 @@
+using Acl.Application;
+
+namespace Acl.Infrastructure;
+
+public sealed class SystemClock : IClock
+{
+    public DateOnly Today => DateOnly.FromDateTime(DateTime.UtcNow);
+}

services/acl/Acl.Infrastructure/ZgwToken.cs

@@ -0,0 +1,29 @@
+using System.Security.Cryptography;
+using System.Text;
+using System.Text.Json;
+
+namespace Acl.Infrastructure;
+
+/// <summary>Mints a ZGW (vng-api-common) JWT: HS256 over the standard claims.</summary>
+internal static class ZgwToken
+{
+    public static string Mint(string clientId, string secret)
+    {
+        var header = B64Url(JsonSerializer.SerializeToUtf8Bytes(new { alg = "HS256", typ = "JWT" }));
+        var payload = B64Url(JsonSerializer.SerializeToUtf8Bytes(new
+        {
+            iss = clientId,
+            iat = DateTimeOffset.UtcNow.ToUnixTimeSeconds(),
+            client_id = clientId,
+            user_id = "acl",
+            user_representation = "acl",
+        }));
+        var signingInput = $"{header}.{payload}";
+        using var hmac = new HMACSHA256(Encoding.UTF8.GetBytes(secret));
+        var signature = B64Url(hmac.ComputeHash(Encoding.UTF8.GetBytes(signingInput)));
+        return $"{signingInput}.{signature}";
+    }
+
+    private static string B64Url(byte[] bytes) =>
+        Convert.ToBase64String(bytes).TrimEnd('=').Replace('+', '-').Replace('/', '_');
+}

services/acl/Acl.Tests/Acl.Tests.csproj

@@ -0,0 +1,26 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="coverlet.collector" Version="6.0.4" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
+    <PackageReference Include="xunit" Version="2.9.3" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="3.1.4" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Using Include="Xunit" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Acl.Application\Acl.Application.csproj" />
+    <ProjectReference Include="..\Acl.Infrastructure\Acl.Infrastructure.csproj" />
+  </ItemGroup>
+
+</Project>

services/acl/Acl.Tests/AclServiceTests.cs

@@ -0,0 +1,47 @@
+using Acl.Application;
+
+namespace Acl.Tests;
+
+public class AclServiceTests
+{
+    private sealed class FakeGateway : IZaakGateway
+    {
+        public ZaakRequest? Captured;
+        public Uri Result { get; } = new("http://openzaak/zaken/api/v1/zaken/abc");
+
+        public Task<Uri> OpenZaakAsync(ZaakRequest request, CancellationToken ct = default)
+        {
+            Captured = request;
+            return Task.FromResult(Result);
+        }
+    }
+
+    private sealed class FixedClock(DateOnly today) : IClock
+    {
+        public DateOnly Today { get; } = today;
+    }
+
+    [Fact]
+    public async Task Opening_a_zaak_default_fills_zgw_fields_and_returns_the_zaak_url()
+    {
+        var gateway = new FakeGateway();
+        var defaults = new AclDefaults
+        {
+            Bronorganisatie = "517439943",
+            VerantwoordelijkeOrganisatie = "517439943",
+            Vertrouwelijkheidaanduiding = "openbaar",
+            ZaaktypeUrl = new("http://openzaak/catalogi/api/v1/zaaktypen/big"),
+        };
+        var service = new AclService(gateway, defaults, new FixedClock(new DateOnly(2026, 6, 4)));
+
+        var url = await service.OpenZaakAsync(new DomainRegistration("123456782"));
+
+        Assert.Equal(gateway.Result, url);
+        var req = Assert.IsType<ZaakRequest>(gateway.Captured);
+        Assert.Equal("517439943", req.Bronorganisatie);
+        Assert.Equal("517439943", req.VerantwoordelijkeOrganisatie);
+        Assert.Equal("openbaar", req.Vertrouwelijkheidaanduiding);
+        Assert.Equal(defaults.ZaaktypeUrl, req.Zaaktype);
+        Assert.Equal(new DateOnly(2026, 6, 4), req.Startdatum);
+    }
+}

services/acl/Acl.Tests/OpenZaakGatewayTests.cs

@@ -0,0 +1,51 @@
+using System.Net;
+using System.Net.Http.Json;
+using Acl.Application;
+using Acl.Infrastructure;
+
+namespace Acl.Tests;
+
+public class OpenZaakGatewayTests
+{
+    private sealed class StubHandler(Func<HttpRequestMessage, Task<HttpResponseMessage>> onSend)
+        : HttpMessageHandler
+    {
+        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken ct)
+            => onSend(request);
+    }
+
+    [Fact]
+    public async Task Posts_zaak_to_openzaak_with_bearer_and_default_fields_and_returns_url()
+    {
+        HttpRequestMessage? seen = null;
+        string? body = null;
+        var handler = new StubHandler(async req =>
+        {
+            seen = req;
+            body = await req.Content!.ReadAsStringAsync();
+            return new HttpResponseMessage(HttpStatusCode.Created)
+            {
+                Content = JsonContent.Create(new { url = "http://openzaak/zaken/api/v1/zaken/xyz" }),
+            };
+        });
+        var gateway = new OpenZaakGateway(
+            new HttpClient(handler),
+            new OpenZaakOptions { BaseUrl = new("http://openzaak"), ClientId = "cid", Secret = "sec" });
+        var request = new ZaakRequest(
+            "517439943", "517439943", "openbaar",
+            new("http://openzaak/catalogi/api/v1/zaaktypen/big"), new DateOnly(2026, 6, 4));
+
+        var url = await gateway.OpenZaakAsync(request);
+
+        Assert.Equal("http://openzaak/zaken/api/v1/zaken/xyz", url.ToString());
+        Assert.Equal(HttpMethod.Post, seen!.Method);
+        Assert.Equal("http://openzaak/zaken/api/v1/zaken", seen.RequestUri!.ToString());
+        Assert.Equal("Bearer", seen.Headers.Authorization!.Scheme);
+        Assert.False(string.IsNullOrWhiteSpace(seen.Headers.Authorization.Parameter));
+        Assert.Contains("\"bronorganisatie\":\"517439943\"", body);
+        Assert.Contains("\"verantwoordelijkeOrganisatie\":\"517439943\"", body);
+        Assert.Contains("\"vertrouwelijkheidaanduiding\":\"openbaar\"", body);
+        Assert.Contains("\"startdatum\":\"2026-06-04\"", body);
+        Assert.Contains("\"zaaktype\":\"http://openzaak/catalogi/api/v1/zaaktypen/big\"", body);
+    }
+}

services/acl/Acl.slnx

@@ -0,0 +1,6 @@
+<Solution>
+  <Project Path="Acl.Api/Acl.Api.csproj" />
+  <Project Path="Acl.Application/Acl.Application.csproj" />
+  <Project Path="Acl.Infrastructure/Acl.Infrastructure.csproj" />
+  <Project Path="Acl.Tests/Acl.Tests.csproj" />
+</Solution>