问Laravel socialite注册如何为用户创建唯一的用户名

EN

  public function redirectToFacebook()
    {
       return Socialite::driver('facebook')->fields([
             'name', 'email', 
        ])->scopes([
            'email'
        ])->redirect();
    } 

    public function handleFacebookCallback()
    {
        try {

            $user = Socialite::driver('facebook')->user();
            $create['name'] = $user->getName();
            $create['email'] = $user->getEmail();
            $create['facebook_id'] = $user->getId();

            $userModel = new User;
            $createdUser = $userModel->addNew($create);
            Auth::loginUsingId($createdUser->id);

            return redirect()->route('/');

        } catch (Exception $e) {

            return redirect('/');
        }
    }