code: func RemoveDeviceFromMulticastGroup(db sqlx.Execer, devEUI lorawan.EUI64, multicastGroupID uuid.UUID) error {
  	res, err := db.Exec(`
  		delete from
  			device_multicast_group
  		where
  			dev_eui = $1
  			and multicast_group_id = $2`,
  		devEUI[:],
  		multicastGroupID,
  	)
  	if err != nil {
  		return handlePSQLError(err, "delete error")
  	}
  
  	ra, err := res.RowsAffected()
  	if err != nil {
  		return handlePSQLError(err, "get rows affected error")
  	}
  
  	if ra == 0 {
  		return ErrDoesNotExist
  	}
  
  	log.WithFields(log.Fields{
  		"dev_eui":            devEUI,
  		"multicast_group_id": multicastGroupID,
  	}).Info("device removed from multicast-group")
  
  	return nil
  }
docs: // RemoveDeviceFromMulticastGroup removes the given device from the given
  // multicast-group.