lib/config/options: fix mqttServer options

nix/lib/config/options.nix

@@ -583,11 +583,11 @@ in
         type = types.str;
         default = config.site.net.serv.hosts4.broker;
       };
-      user = {
+      user = mkOption {
         type = types.str;
         default = "user";
       };
-      password = {
+      password = mkOption {
         type = types.str;
         default = "secret";
       };