public IActionResult InviteUser(int userGroupId, int userId)
        {
            //? maybe there should be some form of invitations/requests to join groups
            try
            {
                _userGroupService.AddInvitation(userId, userGroupId);


                return(Ok($"Invitation sent to user with Id: {userId}"));
            }
            catch (AppException ex)
            {
                // return error message if there was an exception
                return(BadRequest(new { message = ex.Message }));
            }
        }