S-19a · ACL writes the RegisterRecord to Objecten on approval (closes #149) (#151)

Closes #149.

**Outcome:** approving a registration now writes the canonical register record to the **Objecten** API as a `RegisterRecord` object, alongside the ZGW eindstatus. OpenZaak holds the process, Objecten holds the register (ADR-0028). The write goes through the ACL (§8.1) and is idempotent on the zaak id, so a replayed approval updates the existing object rather than creating a second one.

S-19 (#20) was split first (CLAUDE.md §13) — it bundled this with re-sourcing the read projection, which is now #150.

### What landed

- `IRegisterRecordGateway` + `RegisterRecord` in `Acl.Application`; `ObjectenGateway` in `Acl.Infrastructure` (static Token auth, CRS headers, objecttype resolved by name to its highest **published** version).
- `AclService.ApproveZaakAsync` writes the record after the eindstatus, keyed on the zaak UUID with the zaak's identificatie as reference.
- Compose wiring for both stacks; `ADR-0028`; demo note; PRD §15 out-of-scope line retired.

### Three things only a live stack found

Running the gateway against a real Objecten + Objecttypen pair while writing this turned up blockers CI would have hit after the fact:

1. **Objecten rejects an objecttype it has not been configured with**, by UUID — assigned at seed time by a one-shot that runs *after* Objecten's static setup_configuration. The UUID is now pinned on both sides.
2. **Objecten 500s on every write when its Notificaties config is absent** (`notifications_api_common` raises rather than skipping). Objecten → NRC has no broker, worker, kanaal or abonnement, so notifications are **disabled** rather than wired to drop every message; #150 turns them on for real.
3. **Objecttypen echoes the request Host into the objecttype `url`**, and Objecten only accepts the one matching its configured `api_root` — so the ACL must read Objecttypen at `http://objecttypen:8000`. This is why the new integration test only passes inside the compose network.

All three are recorded in ADR-0028.

### Verification

- `ObjectenGatewayIntegrationTests` (verify-acl, in-network): two writes for one id leave exactly one object with the second write's status. **Passing locally against live Objecten.**
- The **Playwright happy path** asserts, after the behandelaar approves, that Objecten holds exactly one `RegisterRecord` for *that* reference — missing, duplicated, or non-public-safe all fail.
- ACL mutation score **92.23%** (baseline 91.37%, break 90).
- `make lint` / `make unit` green locally; full-stack `make verify` runs in CI.

## Definition of Done

- [x] A linked Gitea issue exists (#149).
- [x] Failing test written and committed first.
- [x] Implementation makes the test pass.
- [x] Refactor commit follows if structure improved.
- [x] Conventional Commit messages referencing the issue (`refs #149`).
- [x] All Gitea Actions CI jobs green (run 684).
- [x] `docker compose up` from a fresh clone reaches green health checks within 3 minutes (verify-stack step 1).
- [x] Docs touched — ADR-0028, demo note, PRD §15, BACKLOG.
- [x] ADR added: `docs/architecture/adr-0028-objecten-holds-the-register.md`.
- [x] Demo note appended to `docs/demo-script.md`.
- [x] Closed by the merging PR (`closes #149`).

🤖 Generated with [Claude Code](https://claude.com/claude-code)Reviewed-on: #151

services/acl/Acl.Application/AclService.cs

@@ -2,7 +2,12 @@ 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, IDefaultFillStore fill, IZaaktypeCatalog catalog, IClock clock)
+public sealed class AclService(
+    IZaakGateway gateway,
+    IRegisterRecordGateway register,
+    IDefaultFillStore fill,
+    IZaaktypeCatalog catalog,
+    IClock clock)
 {
     public async Task<Uri> OpenZaakAsync(DomainRegistration registration, CancellationToken ct = default)
     {
@@ -23,16 +28,33 @@ public sealed class AclService(IZaakGateway gateway, IDefaultFillStore fill, IZa
     }
 
     /// <summary>
-    /// Approve a zaak: set it to the eindstatus of the BIG zaaktype (resolved by identificatie, S-27).
-    /// The domain hands over only the zaak URL; the ACL owns which statustype means "approved" (§8.1).
+    /// Approve a zaak: set it to the eindstatus of the BIG zaaktype (resolved by identificatie, S-27),
+    /// then write the register record to Objecten (S-19a). The domain hands over only the zaak URL; the
+    /// ACL owns which statustype means "approved" and what the register record looks like (§8.1).
     /// </summary>
+    /// <remarks>
+    /// OpenZaak holds the process, Objecten holds the register (ADR-0028), so approval is two writes
+    /// across two modules and is eventually consistent by construction. Both are idempotent — a status
+    /// is a log entry, the record upsert is keyed on the zaak id — so a caller that retries a failed
+    /// approval converges rather than duplicating.
+    /// </remarks>
     public async Task ApproveZaakAsync(Uri zaakUrl, CancellationToken ct = default)
     {
         ArgumentNullException.ThrowIfNull(zaakUrl);
 
         await gateway.SetZaakToEindstatusAsync(zaakUrl, await catalog.GetZaaktypeUrlAsync(ct), clock.Today, ct);
+
+        await register.UpsertAsync(
+            new RegisterRecord(
+                ZaakId(zaakUrl),
+                RegisterRecordStatus.Ingeschreven,
+                await gateway.GetZaakIdentificatieAsync(zaakUrl, ct)),
+            ct);
     }
 
+    /// <summary>The zaak's UUID — the key the register record and the read projection rows share.</summary>
+    private static string ZaakId(Uri zaakUrl) => zaakUrl.Segments[^1].TrimEnd('/');
+
     /// <summary>
     /// Cancel a zaak on document-timeout expiry (S-10c): set it to the BIG zaaktype's cancellation
     /// statustype + resultaat. The domain hands over only the zaak URL; the ACL owns which

services/acl/Acl.Application/IRegisterRecordGateway.cs

@@ -0,0 +1,30 @@
+namespace Acl.Application;
+
+/// <summary>
+/// Port to the Objecten API, which holds the authoritative register record (S-19a, ADR-0028).
+/// Implemented in Infrastructure — as with ZGW, the ACL is the only code that talks to the
+/// upstream Common Ground module (§8.1).
+/// </summary>
+public interface IRegisterRecordGateway
+{
+    /// <summary>
+    /// Write the register record for a registration, creating it if absent and updating it if it
+    /// already exists. Idempotent on <see cref="RegisterRecord.Id"/>: a replayed approval updates
+    /// the existing object instead of creating a second one (§8.6).
+    /// </summary>
+    Task UpsertAsync(RegisterRecord record, CancellationToken ct = default);
+}
+
+/// <summary>
+/// The public-safe register record, matching the <c>RegisterRecord</c> objecttype schema registered
+/// in S-18c (ADR-0027). No bsn, no name — the register is world-readable.
+/// </summary>
+public sealed record RegisterRecord(string Id, string Status, string? Reference);
+
+/// <summary>The register statuses the RegisterRecord objecttype's schema allows (ADR-0027).</summary>
+public static class RegisterRecordStatus
+{
+    public const string Ingediend = "INGEDIEND";
+
+    public const string Ingeschreven = "INGESCHREVEN";
+}