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.Clusters/EntKube.Clusters.http

@@ -0,0 +1,6 @@
+@EntKube.Clusters_HostAddress = http://localhost:5243
+
+GET {{EntKube.Clusters_HostAddress}}/weatherforecast/
+Accept: application/json
+
+###