fetchNextcloudApp: add pkgs.test

pkgs/build-support/fetchnextcloudapp/default.nix

···
         exit 1
       fi
     '';
-    # Optionally set name if appName and appVersion are provided
   }
   // lib.optionalAttrs (appName != null && appVersion != null) {
     name = "nextcloud-app-${appName}-${appVersion}";

pkgs/test/default.nix

···
   fetchDebianPatch = recurseIntoAttrs (callPackages ../build-support/fetchdebianpatch/tests.nix { });
   fetchzip = recurseIntoAttrs (callPackages ../build-support/fetchzip/tests.nix { });
   fetchgit = recurseIntoAttrs (callPackages ../build-support/fetchgit/tests.nix { });
+  fetchNextcloudApp = recurseIntoAttrs (
+    callPackages ../build-support/fetchnextcloudapp/tests.nix { }
+  );
   fetchFromBitbucket = recurseIntoAttrs (callPackages ../build-support/fetchbitbucket/tests.nix { });
   fetchFirefoxAddon = recurseIntoAttrs (
     callPackages ../build-support/fetchfirefoxaddon/tests.nix { }