Implement termintating workspace to ensure cleanup logic

Terminating workspaces have landed within KCP https://docs.kcp.io/kcp/main/concepts/workspaces/workspace-termination/. With this we are now able to properly clean up the work, an initializer has done once the corresponding workspace gets deleted. Currently this means we can:

1. Delete the store resources
2. Delete the Keycloak configuration
3. Delete tuples written for a given entity in fga