code: func GroupAddMember(ctx context.Context, groupName, uid string) error {
  	if uid == "" {
  		return constants.ErrEmptyUID
  	}
  	logger.Log.Debugf("Add user to group %s, UID=%d", groupName, uid)
  	return groupServiceInstance.GroupAddMember(ctx, groupName, uid)
  }
docs: // GroupAddMember adds UID to group