Add unit tests for KubernetesCluster, Tenant, ServiceInstance, and RegisterClusterHandler

- Implement tests for KubernetesCluster including registration, connectivity status, and error handling.
- Create tests for Tenant creation, member management, and status changes.
- Add tests for ServiceInstance provisioning and state management.
- Introduce RegisterClusterHandler tests to validate registration requests and error scenarios.
- Set up project files for new test projects with necessary dependencies.

src/EntKube.Provisioning/Infrastructure/InMemoryServiceInstanceRepository.cs

@@ -0,0 +1,41 @@
+using EntKube.Provisioning.Domain;
+
+namespace EntKube.Provisioning.Infrastructure;
+
+/// <summary>
+/// In-memory implementation of the service instance repository for local development.
+/// Production will use EF Core with PostgreSQL.
+/// </summary>
+public class InMemoryServiceInstanceRepository : IServiceInstanceRepository
+{
+    private readonly List<ServiceInstance> instances = new();
+
+    public Task<ServiceInstance?> GetByIdAsync(Guid id, CancellationToken ct = default)
+    {
+        ServiceInstance? instance = instances.FirstOrDefault(i => i.Id == id);
+        return Task.FromResult(instance);
+    }
+
+    public Task<IReadOnlyList<ServiceInstance>> GetByClusterIdAsync(Guid clusterId, CancellationToken ct = default)
+    {
+        IReadOnlyList<ServiceInstance> result = instances.Where(i => i.ClusterId == clusterId).ToList().AsReadOnly();
+        return Task.FromResult(result);
+    }
+
+    public Task<IReadOnlyList<ServiceInstance>> GetAllAsync(CancellationToken ct = default)
+    {
+        IReadOnlyList<ServiceInstance> result = instances.AsReadOnly();
+        return Task.FromResult(result);
+    }
+
+    public Task AddAsync(ServiceInstance instance, CancellationToken ct = default)
+    {
+        instances.Add(instance);
+        return Task.CompletedTask;
+    }
+
+    public Task UpdateAsync(ServiceInstance instance, CancellationToken ct = default)
+    {
+        return Task.CompletedTask;
+    }
+}