test(acl): approving a zaak sets it to the zaaktype's eindstatus, dated today (refs #75)

Red: AclService.ApproveZaakAsync and IZaakGateway.SetZaakToEindstatusAsync don't exist yet.

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

services/acl/Acl.Tests/AclServiceTests.cs

@@ -9,12 +9,28 @@ public class AclServiceTests
         public ZaakRequest? Captured;
         public Uri Result { get; } = new("http://openzaak/zaken/api/v1/zaken/abc");
 
+        public (Uri Zaak, Uri Zaaktype, DateOnly Datum)? Approved;
+
         public Task<Uri> OpenZaakAsync(ZaakRequest request, CancellationToken ct = default)
         {
             Captured = request;
             return Task.FromResult(Result);
         }
+
+        public Task SetZaakToEindstatusAsync(Uri zaakUrl, Uri zaaktypeUrl, DateOnly datumStatusGezet, CancellationToken ct = default)
+        {
+            Approved = (zaakUrl, zaaktypeUrl, datumStatusGezet);
+            return Task.CompletedTask;
         }
+    }
+
+    private static AclDefaults Defaults() => new()
+    {
+        Bronorganisatie = "517439943",
+        VerantwoordelijkeOrganisatie = "517439943",
+        Vertrouwelijkheidaanduiding = "openbaar",
+        ZaaktypeUrl = new("http://openzaak/catalogi/api/v1/zaaktypen/big"),
+    };
 
     private sealed class FixedClock(DateOnly today) : IClock
     {
@@ -61,4 +77,30 @@ public class AclServiceTests
         await Assert.ThrowsAsync<ArgumentNullException>(() => service.OpenZaakAsync(null!));
         Assert.Null(gateway.Captured);
     }
+
+    [Fact]
+    public async Task Approving_a_zaak_sets_it_to_its_zaaktypes_eindstatus_dated_today()
+    {
+        var gateway = new FakeGateway();
+        var defaults = Defaults();
+        var service = new AclService(gateway, defaults, new FixedClock(new DateOnly(2026, 6, 4)));
+        var zaak = new Uri("http://openzaak/zaken/api/v1/zaken/abc");
+
+        await service.ApproveZaakAsync(zaak);
+
+        Assert.NotNull(gateway.Approved);
+        Assert.Equal(zaak, gateway.Approved!.Value.Zaak);
+        Assert.Equal(defaults.ZaaktypeUrl, gateway.Approved.Value.Zaaktype);
+        Assert.Equal(new DateOnly(2026, 6, 4), gateway.Approved.Value.Datum);
+    }
+
+    [Fact]
+    public async Task Approving_a_null_zaak_is_rejected_without_touching_the_gateway()
+    {
+        var gateway = new FakeGateway();
+        var service = new AclService(gateway, Defaults(), new FixedClock(new DateOnly(2026, 6, 4)));
+
+        await Assert.ThrowsAsync<ArgumentNullException>(() => service.ApproveZaakAsync(null!));
+        Assert.Null(gateway.Approved);
+    }
 }