江湖救急，如何将 dingo+passport 实现 passport 的所有路由也带有 API 前缀？

<?php

namespace App\Services;

use Illuminate\Support\Facades\Route;
use Laravel\Passport\Passport;
use Laravel\Passport\RouteRegistrar;

class PassportRouterService extends Passport
{

    /**
     * Binds the Passport routes into the controller.
     *
     * @param  callable|null  $callback
     * @param  array  $options
     * @return void
     */
    public static function routes($callback = null, array $options = [])
    {
        $callback = $callback ?: function ($router) {
            $router->all();
        };

        $defaultOptions = [
            'prefix' => 'api/oauth',         //修改这里的前缀
            'namespace' => '\Laravel\Passport\Http\Controllers',
        ];

        $options = array_merge($defaultOptions, $options);

        Route::group($options, function ($router) use ($callback) {
            $callback(new RouteRegistrar($router));
        });
    }

}

class AuthServiceProvider extends ServiceProvider
{
    ...

    public function boot()
    {
        $this->registerPolicies();
      - Passport::routes();
      + PassportRouterService::routes();    
    }
}