Extend the Woocommerce REST API (with authentication)

class-extend-endpoint.php

<?php

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

class Sample_Extend_Endpoint extends WC_REST_Controller {

	protected $namespace = 'wc/v3';

	protected $rest_base = 'sample_endpoint';

	public function register_routes() {
		register_rest_route( $this->namespace, '/' . $this->rest_base, array(
			'methods'             => WP_REST_Server::EDITABLE,
			'callback'            => array( $this, 'callback_action' ),
			'permission_callback' => array( $this, 'callback_action_permissions_check' ),
			'args'                => $this->get_collection_params(),
		) );
	}

	public function callback_action($request) {
		return json_encode($request->get_params());
	}

	public function callback_action_permissions_check( $request ) {
		$id = (int) $request['id'];

		if ( ! wc_rest_check_user_permissions( 'edit', $id ) ) {
			return new WP_Error( 'woocommerce_rest_cannot_edit', __( 'Sorry, you cannot edit this resource.', 'woocommerce' ), array( 'status' => rest_authorization_required_code() ) );
		}

		return true;
	}

}

main-plugin.php

<?php
class Sample_Plugin {

    public function __construct() {
        $this->init();
    }
    
    public function init() {
        add_filter( 'rest_api_init', array( $this, 'init_extend_endpoint' ) );   
    }
    
    public function init_extend_endpoint() {
      include_once get_stylesheet_directory() . '/class-extend-endpoint.php';
      $save_template = new Sample_Extend_Endpoint();
      $save_template->register_routes();
    }
}