actually pass a priority level fitting my description

services/fediversity/default.nix

@@ -65,4 +65,16 @@ in
       };
     };
   };
+
+  config = {
+    ## FIXME: This should clearly go somewhere else; and we should have a
+    ## `staging` vs. `production` setting somewhere.
+    # use a priority higher than mkDefault for panel deployment to work,
+    # yet lower than default so this will not clash with the setting in tests.
+    security.acme = lib.modules.mkOverride 900 {
+      acceptTerms = true;
+      defaults.email = "something@fediversity.net";
+      # defaults.server = "https://acme-staging-v02.api.letsencrypt.org/directory";
+    };
+  };
 }