code: @SuppressWarnings("WeakerAccess")
      public void pushFcmRegistrationId(String fcmId, boolean register) {
          pushDeviceToken(fcmId, register, PushType.FCM);
      }
docs: Sends the FCM registration ID to CleverTap.
  
  @param fcmId    The FCM registration ID
  @param register Boolean indicating whether to register
  or not for receiving push messages from CleverTap.
  Set this to true to receive push messages from CleverTap,
  and false to not receive any messages from CleverTap.