test(bff): endpoints, JWT auth and public-safe projection (refs #8)

Failing tests for the BFF walking-skeleton endpoints:
- POST /self-service/registrations rejects missing/malformed/wrong-key/expired
  tokens (401) and, with a valid digid token, forwards the bsn to the domain and
  returns 202 (WebApplicationFactory + a local test signing key, ADR-0010).
- GET /openbaar/register serves public-safe rows anonymously (never the bsn) and
  filters by q.
- OpenbaarProjection.PublicView (pure) filters by id and maps to id+status only.

Endpoints and PublicView are stubs so the tests compile and fail on their
assertions; the green commit implements them.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

services/bff/Bff.Api/Bff.Api.csproj

@@ -6,4 +6,10 @@
     <ImplicitUsings>enable</ImplicitUsings>
   </PropertyGroup>
 
+  <ItemGroup>
+    <!-- OIDC/JWT validation of Keycloak-issued tokens (ADR-0010) and OpenAPI generation. -->
+    <PackageReference Include="Microsoft.AspNetCore.Authentication.JwtBearer" Version="10.0.8" />
+    <PackageReference Include="Microsoft.AspNetCore.OpenApi" Version="10.0.8" />
+  </ItemGroup>
+
 </Project>

services/bff/Bff.Api/DownstreamClients.cs

@@ -0,0 +1,47 @@
+using System.Net.Http.Json;
+
+namespace Bff.Api;
+
+/// <summary>What the self-service submit returns to the portal (the domain's registration id + status).</summary>
+public sealed record SubmitAccepted(string RegistrationId, string Status);
+
+/// <summary>A projection row as the projection-api serves it. <c>Bsn</c>/<c>NaamPlaceholder</c> are
+/// read but never surfaced by the openbaar endpoint (public-safe filtering, ADR-0010/S-09).</summary>
+public sealed record ProjectionEntry(string Id, string Status, string? Bsn, string? NaamPlaceholder);
+
+/// <summary>A public-safe openbaar register row — only non-sensitive fields leave the BFF.</summary>
+public sealed record OpenbaarEntry(string Id, string Status);
+
+/// <summary>Port to the Domain Service (§8.3: the BFF is the portals' only backend; it fans out).</summary>
+public interface IDomainClient
+{
+    Task<SubmitAccepted> SubmitRegistrationAsync(string bsn, CancellationToken ct = default);
+}
+
+/// <summary>Port to the read projection.</summary>
+public interface IProjectionClient
+{
+    Task<IReadOnlyList<ProjectionEntry>> GetRegisterAsync(CancellationToken ct = default);
+}
+
+/// <summary>Calls the Domain Service's <c>POST /registrations</c>.</summary>
+public sealed class DomainClient(HttpClient http) : IDomainClient
+{
+    public async Task<SubmitAccepted> SubmitRegistrationAsync(string bsn, CancellationToken ct = default)
+    {
+        using var response = await http.PostAsJsonAsync("registrations", new { bsn }, ct);
+        response.EnsureSuccessStatusCode();
+        var dto = await response.Content.ReadFromJsonAsync<DomainResponse>(ct)
+            ?? throw new InvalidOperationException("The Domain Service returned an empty registration response.");
+        return new SubmitAccepted(dto.RegistrationId, dto.Status);
+    }
+
+    private sealed record DomainResponse(string RegistrationId, string Status, string? ZaakUrl);
+}
+
+/// <summary>Calls the projection-api's <c>GET /register</c>.</summary>
+public sealed class ProjectionClient(HttpClient http) : IProjectionClient
+{
+    public async Task<IReadOnlyList<ProjectionEntry>> GetRegisterAsync(CancellationToken ct = default)
+        => await http.GetFromJsonAsync<List<ProjectionEntry>>("register", ct) ?? [];
+}

services/bff/Bff.Api/OpenbaarProjection.cs

@@ -0,0 +1,15 @@
+namespace Bff.Api;
+
+/// <summary>
+/// The public view of the read projection: filters rows by the openbaar search term and maps each to
+/// a public-safe <see cref="OpenbaarEntry"/> (only <c>id</c> + <c>status</c> — bsn/naam never leave the
+/// BFF). Pure so it is unit- and mutation-tested directly (ADR-0010).
+/// </summary>
+public static class OpenbaarProjection
+{
+    public static IReadOnlyList<OpenbaarEntry> PublicView(IReadOnlyList<ProjectionEntry> entries, string? q)
+    {
+        // STUB (red): returns nothing until the green commit implements filter + public-safe mapping.
+        return [];
+    }
+}

services/bff/Bff.Api/Program.cs

@@ -1,10 +1,44 @@
+using Bff.Api;
+using Microsoft.AspNetCore.Authentication.JwtBearer;
+
 var builder = WebApplication.CreateBuilder(args);
+
+var keycloakAuthority = builder.Configuration["Keycloak:Authority"]
+    ?? throw new InvalidOperationException("Missing configuration 'Keycloak:Authority'");
+var domainBaseUrl = builder.Configuration["Downstream:Domain:BaseUrl"]
+    ?? throw new InvalidOperationException("Missing configuration 'Downstream:Domain:BaseUrl'");
+var projectionBaseUrl = builder.Configuration["Downstream:Projection:BaseUrl"]
+    ?? throw new InvalidOperationException("Missing configuration 'Downstream:Projection:BaseUrl'");
+
+// Validate Keycloak-issued tokens (ADR-0010). Audience validation is off for the walking skeleton —
+// Keycloak's audience mapping is a later hardening; signature/issuer/expiry are validated.
+builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
+    .AddJwtBearer(options =>
+    {
+        options.Authority = keycloakAuthority;
+        options.RequireHttpsMetadata = false;
+        options.TokenValidationParameters.ValidateAudience = false;
+    });
+builder.Services.AddAuthorization();
+
+// The BFF is the portals' only backend; it fans out to the domain and projection (§8.3).
+builder.Services.AddHttpClient<IDomainClient, DomainClient>(c => c.BaseAddress = new Uri(domainBaseUrl));
+builder.Services.AddHttpClient<IProjectionClient, ProjectionClient>(c => c.BaseAddress = new Uri(projectionBaseUrl));
+
 builder.Services.AddHealthChecks();
+builder.Services.AddOpenApi();
 
 var app = builder.Build();
 
-app.MapGet("/", () => "BFF placeholder");
+app.UseAuthentication();
+app.UseAuthorization();
+
 app.MapHealthChecks("/health");
+app.MapOpenApi();
+
+// STUB (red): no auth requirement, no downstream call, no filtering.
+app.MapPost("/self-service/registrations", () => Results.Ok());
+app.MapGet("/openbaar/register", (string? q) => Results.Ok(Array.Empty<OpenbaarEntry>()));
 
 app.Run();
 

services/bff/Bff.Api/appsettings.json

@@ -5,5 +5,12 @@
       "Microsoft.AspNetCore": "Warning"
     }
   },
-  "AllowedHosts": "*"
+  "AllowedHosts": "*",
+  "Keycloak": {
+    "Authority": "http://localhost:8180/realms/digid"
+  },
+  "Downstream": {
+    "Domain": { "BaseUrl": "http://localhost:8130/" },
+    "Projection": { "BaseUrl": "http://localhost:8120/" }
+  }
 }