Some repository refactors (#17950)

* some repository refactors

* remove unnecessary code

* Fix test

* Remove unnecessary banner

services/cron/tasks_extended.go

@@ -118,7 +118,7 @@ func registerRemoveRandomAvatars() {
 		RunAtStart: false,
 		Schedule:   "@every 72h",
 	}, func(ctx context.Context, _ *user_model.User, _ Config) error {
-		return models.RemoveRandomAvatars(ctx)
+		return repo_service.RemoveRandomAvatars(ctx)
 	})
 }