Use a yaml defined route

Closes #3529854

src/Routing/Routes.php

-<?php
-
-namespace Drupal\jsonapi_menu_items\Routing;
-
-use Drupal\Core\DependencyInjection\ContainerInjectionInterface;
-use Drupal\jsonapi_menu_items\Resource\MenuItemsResource;
-use Symfony\Component\DependencyInjection\ContainerInterface;
-use Symfony\Component\Routing\Route;
-use Symfony\Component\Routing\RouteCollection;
-
-/**
- * Defines dynamic routes.
- *
- * Each Menu will result in a jsonapi resource at:
- * /{jsonapi_namespace}/menu_items/{menu_id}
- */
-class Routes implements ContainerInjectionInterface {
-  const RESOURCE_NAME = MenuItemsResource::class;
-  const JSONAPI_RESOURCE_KEY = '_jsonapi_resource';
-
-  /**
-   * {@inheritdoc}
-   */
-  public function __construct() {}
-
-  /**
-   * {@inheritdoc}
-   */
-  public static function create(ContainerInterface $container) {
-    return new static();
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public function routes() {
-    $routes = new RouteCollection();
-
-    $route = new Route('/%jsonapi%/menu_items/{menu}');
-    $route->addDefaults([
-      static::JSONAPI_RESOURCE_KEY => static::RESOURCE_NAME,
-    ]);
-    $route->setOption('parameters', [
-      'menu' => [
-        'type' => 'entity:menu',
-      ],
-    ]);
-    $routes->add('jsonapi_menu_items.menu', $route);
-    $routes->addRequirements(['_access' => 'TRUE']);
-
-    return $routes;
-  }
-
-}