@classmethod
  @gen.coroutine
  def SendRegisterAlert(cls, client, register_user_id, target_user_id, target_settings):
    if target_settings.push_alerts is not None and target_settings.push_alerts != AccountSettings.PUSH_NONE:
      if register_user_id != target_user_id:
        target_name = yield AlertManager._GetNameFromUserId(client, register_user_id, prefer_given_name=False)
        alert_text = '%s has joined Viewfinder' % target_name

        yield AlertManager._SendDeviceAlert(client,
                                            target_user_id,
                                            viewpoint_id=None,
                                            badge=None,
                                            alert_text=alert_text,
                                            sound=PushNotification.DEFAULT_SOUND)
Sends alert to the specified target user, notifying him that one of his contacts has
dataset/ETHPy150Open viewfinderco/viewfinder/backend/op/alert_manager.py/AlertManager.SendRegisterAlert