clanModules/mumble: remove default user

checks/mumble/default.nix

@@ -6,6 +6,9 @@
       {
         imports = [
           self.clanModules.mumble
+          {
+            clan.services.mumble.user = "alice";
+          }
           self.nixosModules.clanCore
           (self.inputs.nixpkgs + "/nixos/tests/common/x11.nix")
           {

clanModules/mumble/default.nix

@@ -28,8 +28,9 @@ in
 {
   options.clan.services.mumble = {
     user = lib.mkOption {
-      type = lib.types.str;
-      default = "alice";
+      type = lib.types.nullOr lib.types.str;
+      default = null;
+      example = "alice";
       description = "The user mumble should be set up for.";
     };
   };