public User UserDelete(User user)
        {
            if (user == null)
            {
                throw new ArgumentNullException(nameof(user), "must not be null.");
            }

            if (!user.Validate())
            {
                throw new ValidationException(nameof(User), user.ValidationResults);
            }

            TaskUtil.Await(identityUserRepository.DeleteAsync(user));

            return(FindById(user.Id));
        }