public IActionResult ApproveTopic(long id)
        {
            if (!User.IsInRole("Admin"))
            {
                return(RedirectToAction("Index", "Home"));
            }

            var result = _paperRepository.SetStatusTopicApproved(id);

            if (result == 1)
            {
                StatusMessage = "Succesfully approved.";
                return(RedirectToAction(nameof(Index)));
            }
            else
            {
                StatusMessage = "Error. You can approve only new topics!";
                return(RedirectToAction(nameof(Index)));
            }
        }