test(acl): integration test opens a real zaak against OpenZaak (refs #46)

S-04a: the deferred S-04 acceptance criterion. A gated Acl.IntegrationTests
project (Category=Integration) drives the real OpenZaakGateway against the
running compose stack — real ZGW JWT auth and the real POST /zaken contract a
stubbed HttpMessageHandler cannot exercise. The lane is kept out of the fast
checks: make unit filters Category!=Integration, Stryker is pinned to Acl.Tests,
and a new make integration target brings the stack up, seeds a published zaaktype
and tears down.

Red: against real OpenZaak the gateway POST fails 400 — JsonContent streams the
body chunked and OpenZaak's uwsgi rejects it. Fixed in the next commit.

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

services/acl/Acl.IntegrationTests/Acl.IntegrationTests.csproj

@@ -0,0 +1,30 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <!-- Integration tests: they talk to a real OpenZaak (the compose stack), so they
+       are gated behind [Trait("Category","Integration")] and excluded from the fast
+       `make unit` / mutation lanes. `make integration` brings the stack up, seeds a
+       published BIG zaaktype (OZ_PUBLISH=1) and runs this project. See ADR-0006. -->
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="coverlet.collector" Version="6.0.4" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
+    <PackageReference Include="xunit" Version="2.9.3" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="3.1.4" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Using Include="Xunit" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Acl.Application\Acl.Application.csproj" />
+    <ProjectReference Include="..\Acl.Infrastructure\Acl.Infrastructure.csproj" />
+  </ItemGroup>
+
+</Project>