Woocommerce API REST custom path

wc-api-custom.php

<?php

/**
 * Custom API REST path  class
 *
 * @package MyPlugin
 * @author Skatox
 */
class WC_API_Custom extends WC_API_Resource
{

    const PATH = '/custom';

    /**
     * Function to define each of the custom path
     */
    public function register_routes($routes)
    {
        //GET Request
        $routes[self::PATH . '/orders'] = array(
            array(array($this, 'listShippingOrders'), WC_API_Server::READABLE),
        );

        //POST Request
        $routes[self::PATH . '/orders/(?P<order_id>\d+)/fulfillments.json'] = array(
            array(array($this, 'createItem'), WC_API_Server::CREATABLE | WC_API_Server::ACCEPT_DATA),
        );

        //PUT Request
        $routes[self::PATH . '/variants/(?P<id>\d+).json'] = array(
            array(array($this, 'updateItem'), WC_API_Server::EDITABLE | WC_API_Server::ACCEPT_DATA),
        );

        return $routes;
    }

    public function listShippingOrders($fields = null, $filter = array(), $status = null, $page = 1)
    {
        $wcApiOrders = new WC_API_Orders($this->server);
        $orders = $wcApiOrders->get_orders($fields, $filter, $status, $page);

        //Removes orders without shipping methods
        foreach ($orders['orders'] as $key => $oreder)
        {
            if (empty($oreder['shipping_methods'])) {
                unset($oreders['orders'][$key]);
                continue;
            }
        }

        return $order;
    }

    public function createItem($order_id, $data)
    {
        //Do insert proccess and then return the response array
    }

    public function updateItem($id, $data)
    {
        //Do update proccess and then return the response array

    }
}

woocommerce-extend-api.php

<?php
/**
 * Plugin Name: Woocommerce custom path example
 * Description: Custom API calls plugin
 * Version: 1.0
 * Author: Miguel Useche
 * Author URI: http://migueluseche.com
 * License: GPL 3.0
 * 
 * @package MyPlugin
 */
  
if ( ! defined( 'ABSPATH' ) ) {
	exit; // Exit if accessed directly
}

if (!class_exists('WD_API_LOADER')) {

    /**
     * Main plugin class
     *
     * @package MyPlugin
     * @author Skatox
     */
    class WD_API_LOADER
    {
        public function init()
        {
          add_action( 'woocommerce_api_loaded', array( $this, 'load' ) );
        }

        public function load()
        {
        	require_once plugin_dir_path( __FILE__ ).'wc-api-custom.php';
        	add_filter( 'woocommerce_api_classes', array( $this, 'register' ) );
        }

        public function register( $api_classes=array() )
        {
          array_push( $api_classes, 'WC_API_Custom' );

          return $api_classes;
        }
    }
}

$wc_custom_api = new WD_API_LOADER();
$wc_custom_api->init();