Tryfix Grafana Google Auth

nixos/modules/monitoring/server/grafana.nix

@@ -119,7 +119,7 @@ in {
           # Grafana considers it "sign up" to let in a user it has
           # never seen before.
           allow_sign_up = true;
-          client_secret_file = cfg.googleOAuthClientSecretFile;
+          client_secret = "$__file{${toString cfg.googleOAuthClientSecretFile}}";
           client_id = cfg.googleOAuthClientID;
         };