Use our modified Grafana service definition

nixos/modules/monitoring/server/grafana.nix

@@ -19,6 +19,12 @@ let
                 };
 
 in {
+
+  # Override Grafana module so we can specify datasource UIDs
+  # Copied from https://nixos.org/manual/nixos/stable/#sec-replace-modules
+  disabledModules = [ "services/monitoring/grafana.nix" ];
+  imports = [ ./grafana-service.nix ];
+
   options.services.private-storage.monitoring.grafana = {
     domains = lib.mkOption
     { type = lib.types.listOf lib.types.str;