feat(acl): diploma upload stored in the ZGW Documenten API (S-10b, closes #103) (#108)

## What & why

S-10b: the self-service **diploma upload** is now real. After submitting, the citizen picks a PDF and
uploads it; the portal base64-encodes it client-side → BFF → domain → **ACL**, which stores it in the
ZGW **Documenten (DRC) API** as an `enkelvoudiginformatieobject` and relates it to the zaak, then the
`WachtOpDocumenten` wait completes and the case advances to beoordeling. Per §8.1 only the ACL talks to
ZGW.

Closes #103

Mechanism in **ADR-0018** (proposal #107). Builds on S-10a (#102). The zaak-close-on-expiry item is
carved to **#106 (S-10c)**.

## Definition of Done

- [x] Linked Gitea issue (above).
- [x] Failing test committed before the implementation (red→green per layer).
- [x] Conventional Commits referencing the issue (`refs #103`).
- [ ] CI green — all Gitea Actions jobs (pending on this PR).
- [x] `docker compose up` health unaffected (ACL boots on a placeholder informatieobjecttype URL; the real one is injected by verify-domain).
- [x] Docs updated (ADR-0018, demo-script, BACKLOG + S-10c).
- [x] ADR added (`docs/architecture/adr-0018-diploma-upload-via-acl-documenten.md`).
- [x] Demo note in `docs/demo-script.md`.

## Notes for reviewers

- **ACL** (`OpenZaakGateway.StoreDocumentAsync` + `AclService.StoreDiplomaAsync` + `POST /documenten`) reuses the existing gateway patterns (ZGW Bearer, buffered non-chunked body, **no CRS** — Documenten isn't geo). Unit-tested via the stub handler; an **integration test** stores a real document against live OpenZaak (verify-acl).
- **Transport:** base64 JSON on every hop (portal encodes client-side) — I deviated from proposal #107's multipart to keep one contract shape and avoid `IFormFile`/antiforgery/multipart-client plumbing; fine at diploma size (ADR-0018 §Alternatives).
- **Infra:** `seed_catalogus.py` seeds + publishes a "Diploma" `informatieobjecttype` and relates it to the zaaktype (while both concept); `verify-domain` injects its URL into the ACL. No new ZGW scopes (seed applicatie has `heeft_alle_autorisaties`).
- **e2e:** uploads a real PDF (`setInputFiles`) after the openbaar INGEDIEND row confirms the zaak is open (so storage doesn't race the OpenZaak worker).
- **Scope boundary:** the ZGW zaak is not set to a cancellation status on 30-day expiry — that's #106 (S-10c).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Reviewed-on: #108

services/domain/Big.Api/Program.cs

@@ -120,8 +120,17 @@ app.MapPost("/registrations/{id}/documents", async (string id, ProvideDocumentsR
 
     if (string.IsNullOrWhiteSpace(body?.Bsn))
         return Results.BadRequest(new { error = "A bsn is required to provide documents." });
+    if (string.IsNullOrWhiteSpace(body.ContentBase64))
+        return Results.BadRequest(new { error = "A document is required." });
 
-    var outcome = await provide.HandleAsync(new ProvideDocumentsCommand(new RegistrationId(guid), body.Bsn), ct);
+    byte[] content;
+    try { content = Convert.FromBase64String(body.ContentBase64); }
+    catch (FormatException) { return Results.BadRequest(new { error = "The document content is not valid base64." }); }
+
+    var command = new ProvideDocumentsCommand(
+        new RegistrationId(guid), body.Bsn, content,
+        body.FileName ?? "diploma.pdf", body.ContentType ?? "application/pdf");
+    var outcome = await provide.HandleAsync(command, ct);
     return outcome == ProvideDocumentsOutcome.Accepted ? Results.NoContent() : Results.NotFound();
 });
 
@@ -152,7 +161,7 @@ public sealed record DecideRequest(string Besluit);
 
 public sealed record WithdrawRequest(string Bsn);
 
-public sealed record ProvideDocumentsRequest(string Bsn);
+public sealed record ProvideDocumentsRequest(string Bsn, string ContentBase64, string? FileName = null, string? ContentType = null);
 
 public sealed record RegistrationResponse(string RegistrationId, string Status, string? ZaakUrl);
 

services/domain/Big.Application/Ports.cs

@@ -52,6 +52,13 @@ public interface IAclClient
     /// the zaak's final status — which OpenZaak notifies over NRC; the domain never names statustypen.
     /// </summary>
     Task ApproveZaakAsync(Uri zaakUrl, CancellationToken ct = default);
+
+    /// <summary>
+    /// Store an uploaded diploma against the zaak (S-10b). The domain hands over the zaak, the raw file
+    /// bytes, and the file's name/type; the ACL creates the ZGW informatieobject and relates it to the
+    /// zaak (§8.1). Returns the stored document's URL.
+    /// </summary>
+    Task<Uri> StoreDiplomaAsync(Uri zaakUrl, byte[] content, string fileName, string contentType, CancellationToken ct = default);
 }
 
 /// <summary>

services/domain/Big.Application/ProvideDocuments.cs

@@ -2,10 +2,12 @@ using Big.Domain;
 
 namespace Big.Application;
 
-/// <summary>A zorgprofessional's signal that they have supplied the documents their registration is
-/// waiting for ("documenten aanleveren"). <paramref name="Bsn"/> is the authenticated caller (from the
-/// DigiD token, forwarded by the BFF): only the registration's own bsn may provide its documents.</summary>
-public sealed record ProvideDocumentsCommand(RegistrationId RegistrationId, string Bsn);
+/// <summary>A zorgprofessional's upload of the diploma their registration is waiting for ("documenten
+/// aanleveren"). <paramref name="Bsn"/> is the authenticated caller (from the DigiD token, forwarded by
+/// the BFF): only the registration's own bsn may provide its documents. <paramref name="Content"/> is
+/// the raw file, with its <paramref name="FileName"/> and <paramref name="ContentType"/>.</summary>
+public sealed record ProvideDocumentsCommand(
+    RegistrationId RegistrationId, string Bsn, byte[] Content, string FileName, string ContentType);
 
 /// <summary>The outcome of a provide-documents request.</summary>
 public enum ProvideDocumentsOutcome
@@ -19,14 +21,14 @@ public enum ProvideDocumentsOutcome
 }
 
 /// <summary>
-/// The provide-documents use case (S-10a): a zorgprofessional supplies the documents their registration
-/// is parked waiting for, completing the WachtOpDocumenten task so the registratie process leaves the
-/// 30-day wait and continues to beoordeling (ADR-0017). Owner-scoped by bsn. Completing the wait is
-/// best-effort: if the registration never started a process (or already left the wait), the request
-/// still stands, mirroring how <see cref="WithdrawRegistration"/> cancels best-effort. The actual file
-/// upload and its ZGW storage via the ACL is S-10b; this is the trigger that unblocks the process.
+/// The provide-documents use case (S-10a/S-10b): a zorgprofessional uploads the diploma their
+/// registration is parked waiting for. The document is stored in ZGW via the ACL (§8.1), then the
+/// WachtOpDocumenten task is completed so the registratie process leaves the 30-day wait and continues
+/// to beoordeling (ADR-0017). Owner-scoped by bsn. Both steps are best-effort about missing preconditions
+/// (mirroring <see cref="WithdrawRegistration"/>): storage needs an opened zaak, and completion needs a
+/// running process — a request that arrives before either still stands, storing/completing what it can.
 /// </summary>
-public sealed class ProvideDocuments(IRegistrationStore store, IWorkflowClient workflow)
+public sealed class ProvideDocuments(IRegistrationStore store, IWorkflowClient workflow, IAclClient acl)
 {
     public async Task<ProvideDocumentsOutcome> HandleAsync(ProvideDocumentsCommand command, CancellationToken ct = default)
     {
@@ -38,6 +40,11 @@ public sealed class ProvideDocuments(IRegistrationStore store, IWorkflowClient w
         if (registration is null || registration.Bsn != command.Bsn)
             return ProvideDocumentsOutcome.NotFound;
 
+        // Store the diploma against the zaak (once it is opened) — the ACL is the only ZGW caller (§8.1).
+        if (registration.ZaakUrl is not null)
+            await acl.StoreDiplomaAsync(
+                registration.ZaakUrl, command.Content, command.FileName, command.ContentType, ct);
+
         // Complete the document wait (if a process is running) so beoordeling can proceed.
         if (registration.ProcessInstanceId is not null)
             await workflow.CompleteDocumentWaitAsync(registration.ProcessInstanceId, ct);

services/domain/Big.Infrastructure/AclHttpClient.cs

@@ -31,6 +31,23 @@ public sealed class AclHttpClient(HttpClient http, AclOptions options) : IAclCli
         response.EnsureSuccessStatusCode();
     }
 
+    public async Task<Uri> StoreDiplomaAsync(Uri zaakUrl, byte[] content, string fileName, string contentType, CancellationToken ct = default)
+    {
+        ArgumentNullException.ThrowIfNull(zaakUrl);
+        ArgumentNullException.ThrowIfNull(content);
+
+        // The file crosses this boundary base64-encoded in JSON — the domain and ACL contracts are
+        // JSON, and a diploma is small (S-10b, ADR). The ACL turns it into a ZGW informatieobject.
+        using var response = await http.PostAsJsonAsync(
+            new Uri(options.BaseUrl, "documenten"),
+            new StoreDocumentRequest(zaakUrl.ToString(), Convert.ToBase64String(content), fileName, contentType), ct);
+        response.EnsureSuccessStatusCode();
+
+        var stored = await response.Content.ReadFromJsonAsync<StoreDocumentResponse>(ct)
+            ?? throw new InvalidOperationException("The ACL returned an empty document response.");
+        return new Uri(stored.InformatieobjectUrl);
+    }
+
     private sealed record OpenZaakRequest(
         [property: JsonPropertyName("bsn")] string Bsn,
         [property: JsonPropertyName("reference")] string Reference);
@@ -38,4 +55,13 @@ public sealed class AclHttpClient(HttpClient http, AclOptions options) : IAclCli
     private sealed record OpenZaakResponse([property: JsonPropertyName("zaakUrl")] string ZaakUrl);
 
     private sealed record SetStatusRequest([property: JsonPropertyName("zaakUrl")] string ZaakUrl);
+
+    private sealed record StoreDocumentRequest(
+        [property: JsonPropertyName("zaakUrl")] string ZaakUrl,
+        [property: JsonPropertyName("contentBase64")] string ContentBase64,
+        [property: JsonPropertyName("fileName")] string FileName,
+        [property: JsonPropertyName("contentType")] string ContentType);
+
+    private sealed record StoreDocumentResponse(
+        [property: JsonPropertyName("informatieobjectUrl")] string InformatieobjectUrl);
 }

services/domain/Big.Tests/Fakes.cs

@@ -110,4 +110,13 @@ internal sealed class FakeAclClient(Uri? zaakUrl = null) : IAclClient
         ApprovedZaakUrl = zaakUrl;
         return Task.CompletedTask;
     }
+
+    public (Uri ZaakUrl, byte[] Content, string FileName, string ContentType)? StoredDiploma { get; private set; }
+    public static readonly Uri DefaultDocumentUrl = new("http://openzaak/documenten/api/v1/enkelvoudiginformatieobjecten/doc");
+
+    public Task<Uri> StoreDiplomaAsync(Uri zaakUrl, byte[] content, string fileName, string contentType, CancellationToken ct = default)
+    {
+        StoredDiploma = (zaakUrl, content, fileName, contentType);
+        return Task.FromResult(DefaultDocumentUrl);
+    }
 }

services/domain/Big.Tests/ProvideDocumentsTests.cs

@@ -3,52 +3,60 @@ using Big.Domain;
 
 namespace Big.Tests;
 
-// S-10a (#102): the "documents received" use case. A zorgprofessional supplies the documents their
-// registration is waiting for; the handler completes the WachtOpDocumenten task via the Workflow Client
-// so the process leaves the 30-day wait and continues to beoordeling. Owner-scoped by the caller's bsn,
-// like WithdrawRegistration. (The real file upload + ZGW storage is S-10b; this is the trigger path.)
+// S-10a/S-10b (#102/#103): the "documents received" use case. A zorgprofessional supplies the diploma
+// their registration is waiting for; the handler stores it in ZGW via the ACL and completes the
+// WachtOpDocumenten task via the Workflow Client so the process continues to beoordeling. Owner-scoped
+// by the caller's bsn, like WithdrawRegistration.
 public class ProvideDocumentsTests
 {
     private const string Bsn = "123456782";
+    private static readonly Uri Zaak = new("http://openzaak/zaken/api/v1/zaken/abc");
 
     private static Registration Submitted(string processInstanceId = "proc-1")
     {
         var registration = Registration.Submit(Bsn);
         registration.RecordProcessStarted(processInstanceId);
+        registration.AttachZaak(Zaak);
         return registration;
     }
 
-    private static ProvideDocumentsCommand Command(RegistrationId id, string bsn = Bsn) => new(id, bsn);
+    private static ProvideDocumentsCommand Command(RegistrationId id, string bsn = Bsn) =>
+        new(id, bsn, [1, 2, 3], "diploma.pdf", "application/pdf");
 
     [Fact]
-    public async Task Providing_documents_completes_the_document_wait()
+    public async Task Providing_documents_stores_the_diploma_and_completes_the_wait()
     {
         var store = new FakeRegistrationStore();
         var registration = Submitted("proc-42");
         store.Seed(registration);
         var workflow = new FakeWorkflowClient();
-        var handler = new ProvideDocuments(store, workflow);
+        var acl = new FakeAclClient();
+        var handler = new ProvideDocuments(store, workflow, acl);
 
         var outcome = await handler.HandleAsync(Command(registration.Id));
 
         Assert.Equal(ProvideDocumentsOutcome.Accepted, outcome);
+        // Stored against the registration's zaak, carrying the uploaded bytes + file metadata.
+        Assert.Equal((Zaak, new byte[] { 1, 2, 3 }, "diploma.pdf", "application/pdf"), acl.StoredDiploma);
+        // …and the wait is completed so beoordeling can proceed.
         Assert.Equal("proc-42", workflow.CompletedDocumentWaitFor);
     }
 
     [Fact]
     public async Task A_different_bsn_cannot_provide_documents()
     {
-        // Owner-scoping: only the registration's own bsn may supply its documents. Another bsn is told
-        // NotFound (existence not revealed) and the wait is not completed.
+        // Owner-scoping: another bsn is told NotFound; nothing is stored or completed.
         var store = new FakeRegistrationStore();
         var registration = Submitted();
         store.Seed(registration);
         var workflow = new FakeWorkflowClient();
-        var handler = new ProvideDocuments(store, workflow);
+        var acl = new FakeAclClient();
+        var handler = new ProvideDocuments(store, workflow, acl);
 
         var outcome = await handler.HandleAsync(Command(registration.Id, bsn: "999999990"));
 
         Assert.Equal(ProvideDocumentsOutcome.NotFound, outcome);
+        Assert.Null(acl.StoredDiploma);
         Assert.Null(workflow.CompletedDocumentWaitFor);
     }
 
@@ -56,30 +64,33 @@ public class ProvideDocumentsTests
     public async Task Providing_for_an_unknown_registration_is_not_found()
     {
         var store = new FakeRegistrationStore();
-        var handler = new ProvideDocuments(store, new FakeWorkflowClient());
+        var handler = new ProvideDocuments(store, new FakeWorkflowClient(), new FakeAclClient());
 
         Assert.Equal(ProvideDocumentsOutcome.NotFound, await handler.HandleAsync(Command(RegistrationId.New())));
     }
 
     [Fact]
-    public async Task Providing_before_a_process_started_is_accepted_without_calling_the_workflow()
+    public async Task Providing_before_a_zaak_is_opened_does_not_store_but_still_completes_the_wait()
     {
-        // No process yet → no wait task to complete; the request still stands (best-effort, mirroring
-        // WithdrawRegistration) and the Workflow Client is not called.
+        // No zaak yet → nothing to file the document against, but the request still stands (best-effort,
+        // mirroring WithdrawRegistration). The wait is completed if a process is running.
         var store = new FakeRegistrationStore();
-        var registration = Registration.Submit(Bsn); // no RecordProcessStarted
+        var registration = Registration.Submit(Bsn);
+        registration.RecordProcessStarted("proc-9"); // process started, but no zaak attached
         store.Seed(registration);
         var workflow = new FakeWorkflowClient();
-        var handler = new ProvideDocuments(store, workflow);
+        var acl = new FakeAclClient();
+        var handler = new ProvideDocuments(store, workflow, acl);
 
         var outcome = await handler.HandleAsync(Command(registration.Id));
 
         Assert.Equal(ProvideDocumentsOutcome.Accepted, outcome);
-        Assert.Null(workflow.CompletedDocumentWaitFor);
+        Assert.Null(acl.StoredDiploma);
+        Assert.Equal("proc-9", workflow.CompletedDocumentWaitFor);
     }
 
     [Fact]
     public async Task Rejects_a_null_command()
         => await Assert.ThrowsAsync<ArgumentNullException>(() =>
-            new ProvideDocuments(new FakeRegistrationStore(), new FakeWorkflowClient()).HandleAsync(null!));
+            new ProvideDocuments(new FakeRegistrationStore(), new FakeWorkflowClient(), new FakeAclClient()).HandleAsync(null!));
 }