feat(acl): wire BDD step bindings to AclService (refs #5)

Implement the step definitions for EenZaakOpenen.feature against the
existing AclService, with an in-memory gateway standing in for the OpenZaak
Zaken API. The scenario now passes: a domain registration is default-filled
into a ZaakRequest (ADR-0003) and the created zaak URL is returned.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/acceptance/Steps/EenZaakOpenenSteps.cs

@@ -0,0 +1,65 @@
+using Acceptance.Support;
+using Acl.Application;
+using Reqnroll;
+using Xunit;
+
+namespace Acceptance.Steps;
+
+/// <summary>Bindings for <c>EenZaakOpenen.feature</c>. Reqnroll creates one
+/// instance per scenario, so instance fields hold scenario-scoped state.</summary>
+[Binding]
+public sealed class EenZaakOpenenSteps
+{
+    private readonly InMemoryZaakGateway _gateway = new();
+    private DomainRegistration? _registration;
+    private AclDefaults? _defaults;
+    private DateOnly _today;
+    private Uri? _returnedUrl;
+
+    [Given("a domain registration for BSN \"(.*)\"")]
+    public void GivenADomainRegistrationForBsn(string bsn)
+        => _registration = new DomainRegistration(bsn);
+
+    [Given("the ACL is configured with these defaults:")]
+    public void GivenTheAclIsConfiguredWithTheseDefaults(DataTable defaults)
+    {
+        var values = ToFieldMap(defaults);
+        _defaults = new AclDefaults
+        {
+            Bronorganisatie = values["bronorganisatie"],
+            VerantwoordelijkeOrganisatie = values["verantwoordelijkeOrganisatie"],
+            Vertrouwelijkheidaanduiding = values["vertrouwelijkheidaanduiding"],
+            ZaaktypeUrl = new Uri(values["zaaktype"]),
+        };
+    }
+
+    [Given("today is \"(.*)\"")]
+    public void GivenTodayIs(string date)
+        => _today = DateOnly.Parse(date);
+
+    [When("the domain asks the ACL to open a zaak")]
+    public async Task WhenTheDomainAsksTheAclToOpenAZaak()
+    {
+        var service = new AclService(_gateway, _defaults!, new FixedClock(_today));
+        _returnedUrl = await service.OpenZaakAsync(_registration!);
+    }
+
+    [Then("a zaak is created with these default-filled fields")]
+    public void ThenAZaakIsCreatedWithTheseDefaultFilledFields(DataTable expected)
+    {
+        var request = Assert.IsType<ZaakRequest>(_gateway.Captured);
+        var fields = ToFieldMap(expected);
+        Assert.Equal(fields["bronorganisatie"], request.Bronorganisatie);
+        Assert.Equal(fields["verantwoordelijkeOrganisatie"], request.VerantwoordelijkeOrganisatie);
+        Assert.Equal(fields["vertrouwelijkheidaanduiding"], request.Vertrouwelijkheidaanduiding);
+        Assert.Equal(fields["zaaktype"], request.Zaaktype.ToString());
+        Assert.Equal(fields["startdatum"], request.Startdatum.ToString("yyyy-MM-dd"));
+    }
+
+    [Then("the ACL returns the URL of the created zaak")]
+    public void ThenTheAclReturnsTheUrlOfTheCreatedZaak()
+        => Assert.Equal(InMemoryZaakGateway.CreatedZaakUrl, _returnedUrl);
+
+    private static Dictionary<string, string> ToFieldMap(DataTable table)
+        => table.Rows.ToDictionary(r => r["field"], r => r["value"]);
+}