Zanzana: Setup GRPC authentication in client/server mode (#98680)

* Zanzana: Setup GRPC authentication in client/server mode

* don't use grpcutils

* refactor

Co-authored-by: Karl Persson <kalle.persson@grafana.com>

* Add a namespace stub for in-proc mode

Co-authored-by: Karl Persson <kalle.persson@grafana.com>

* Read parameters from config

* authorize server requests

* add namespace to the tests context

* use stack id from config

* simplify authorize func

* properly format namespace

* return Unauthenticated if namespace is empty

* use insecure cred only in dev env

* check request namespace

* Use CallCredentials API for client auth

* provide config

* fail if stack id is missing

* improve error message

* use insecure connection by default

---------

Co-authored-by: Karl Persson <kalle.persson@grafana.com>

pkg/services/authz/zanzana/server/server_write.go

@@ -13,6 +13,10 @@ func (s *Server) Write(ctx context.Context, req *authzextv1.WriteRequest) (*auth
 	ctx, span := tracer.Start(ctx, "authzServer.Write")
 	defer span.End()
 
+	if err := authorize(ctx, req.GetNamespace()); err != nil {
+		return nil, err
+	}
+
 	storeInf, err := s.getStoreInfo(ctx, req.Namespace)
 	if err != nil {
 		return nil, err