public async Task <Notification> ChangeImportant(string username, int nId, bool important)
        {
            var notification = await notificationRepo.GetById(nId);

            if (notification == null)
            {
                throw new NotFoundException();
            }
            if (username != notification.Username)
            {
                throw new ForbiddenException();
            }
            notification.Important = important;
            return(await notificationRepo.Update(notification));
        }