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_test.go

@@ -4,6 +4,8 @@ import (
 	"context"
 	"testing"
 
+	authnlib "github.com/grafana/authlib/authn"
+	"github.com/grafana/authlib/claims"
 	openfgav1 "github.com/openfga/api/proto/openfga/v1"
 	"github.com/stretchr/testify/require"
 
@@ -102,3 +104,13 @@ func setup(t *testing.T, testDB db.DB, cfg *setting.Cfg) *Server {
 	require.NoError(t, err)
 	return srv
 }
+
+func newContextWithNamespace() context.Context {
+	ctx := context.Background()
+	ctx = claims.WithClaims(ctx, authnlib.NewAccessTokenAuthInfo(authnlib.Claims[authnlib.AccessTokenClaims]{
+		Rest: authnlib.AccessTokenClaims{
+			Namespace: "*",
+		},
+	}))
+	return ctx
+}