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/grpcserver/interceptors/auth.go

@@ -21,6 +21,12 @@ type Authenticator interface {
 	Authenticate(ctx context.Context) (context.Context, error)
 }
 
+type AuthenticatorFunc func(context.Context) (context.Context, error)
+
+func (fn AuthenticatorFunc) Authenticate(ctx context.Context) (context.Context, error) {
+	return fn(ctx)
+}
+
 // authenticator can authenticate GRPC requests.
 type authenticator struct {
 	contextHandler grpccontext.ContextHandler