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

tests/acceptance/Steps/EenZaakOpenenSteps.cs

@@ -30,6 +30,7 @@ public sealed class EenZaakOpenenSteps
             VerantwoordelijkeOrganisatie = values["verantwoordelijkeOrganisatie"],
             Vertrouwelijkheidaanduiding = values["vertrouwelijkheidaanduiding"],
             ZaaktypeUrl = new Uri(values["zaaktype"]),
+            InformatieobjecttypeUrl = new Uri("http://openzaak/catalogi/api/v1/informatieobjecttypen/dip"),
         };
     }
 

tests/acceptance/Support/BffAcceptanceHost.cs

@@ -72,7 +72,8 @@ public sealed class CapturingDomainClient : IDomainClient
     public Task<bool> WithdrawRegistrationAsync(string registrationId, string bsn, CancellationToken ct = default)
         => Task.FromResult(true);
 
-    public Task<bool> ProvideDocumentsAsync(string registrationId, string bsn, CancellationToken ct = default)
+    public Task<bool> ProvideDocumentsAsync(
+        string registrationId, string bsn, string contentBase64, string? fileName, string? contentType, CancellationToken ct = default)
         => Task.FromResult(true);
 
     public Task<IReadOnlyList<WerkbakItem>> GetWerkbakAsync(CancellationToken ct = default)

tests/acceptance/Support/InMemoryDomainPorts.cs

@@ -59,6 +59,14 @@ public sealed class InMemoryAclClient : IAclClient
         ApprovedZaakUrl = zaakUrl;
         return Task.CompletedTask;
     }
+
+    public (Uri ZaakUrl, string FileName)? StoredDiploma { get; private set; }
+
+    public Task<Uri> StoreDiplomaAsync(Uri zaakUrl, byte[] content, string fileName, string contentType, CancellationToken ct = default)
+    {
+        StoredDiploma = (zaakUrl, fileName);
+        return Task.FromResult(new Uri("http://openzaak/documenten/api/v1/enkelvoudiginformatieobjecten/acc-doc"));
+    }
 }
 
 /// <summary>An in-memory user-task client for the beoordeling acceptance scenario: it holds one open

tests/acceptance/Support/InMemoryZaakGateway.cs

@@ -27,4 +27,7 @@ public sealed class InMemoryZaakGateway : IZaakGateway
 
     public Task<string> GetZaakIdentificatieAsync(Uri zaakUrl, CancellationToken ct = default)
         => Task.FromResult("ACC-REF-1");
+
+    public Task<Uri> StoreDocumentAsync(DocumentRequest request, CancellationToken ct = default)
+        => Task.FromResult(new Uri("http://openzaak/documenten/api/v1/enkelvoudiginformatieobjecten/acc-doc"));
 }

tests/e2e/registration.spec.ts

@@ -56,6 +56,11 @@ test('DigiD submit → public INGEDIEND → documenten → behandelaar goedkeurt
   // why we supply the documents here rather than right after submit, when the trigger would race the
   // wait and no-op. (S-10b turns this into a real file upload; here it is the trigger that unblocks
   // beoordeling.)
+  await page.setInputFiles('#diploma', {
+    name: 'diploma.pdf',
+    mimeType: 'application/pdf',
+    buffer: Buffer.from('%PDF-1.4 synthetic diploma\n'),
+  });
   await page.getByRole('button', { name: /documenten aanleveren/i }).click();
   await expect(page.getByText(/documenten zijn aangeleverd/i)).toBeVisible();