public Task AddToRoleAsync(ApplicationUser user, string roleName, CancellationToken cancellationToken)
        {
            if (user == null)
            {
                throw new ArgumentNullException("user");
            }
            if (roleName == "")
            {
                throw new ArgumentNullException("roleName");
            }
            var result = _authService.AddToRole(user.Id, roleName);

            user.ApplicationRoles.Add(result.Item);
            return(Task.FromResult(result.Item));
        }