public function handle($data)
 {
     $this->validate_request(["setting" => ["key", "value"]]);
     $profile = GroupBackend::fetch_group_profile($this->params["id"]);
     $setting = $data->{"setting"};
     GroupBackend::set_group_setting($profile, $setting);
     return ["user" => $profile->toExternalForm(), "setting" => $setting];
 }