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.

.gitea/workflows/build.yaml

@@ -0,0 +1,28 @@
+name: Build EntKube
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup .NET
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: '10.0.x'
+
+      - name: Restore dependencies
+        run: dotnet restore EntKube.slnx
+
+      - name: Build
+        run: dotnet build EntKube.slnx --no-restore --configuration Release
+
+      - name: Test
+        run: dotnet test EntKube.slnx --no-build --configuration Release