How to Create New Callback URL for Whatsapp

<?php
//create route to verify whatsapp url
function whatsapp_verify_register_route(){
    register_rest_route( 'wpcargo-v1', '/whatsapp', array(
        'methods' =>'GET',
        'callback' => 'whatsapp_verification',
        'show_in_index' => false,
        'permission_callback' => '__return_true',
    ));
}
add_action( 'rest_api_init', 'whatsapp_verify_register_route' );

// Generate callback URL Response
function whatsapp_verification(){
    $verify_token = get_option('verify_token') ? get_option('verify_token') : 'whatsapptesttoken123';
    $get_params = $_GET;
    $error = 'Please check you token and verify again';
    if (!empty($get_params)) {
        $mode       = $get_params["hub_mode"];
        $token      = $get_params["hub_verify_token"];
        $challenge  = $get_params["hub_challenge"];

        if (!empty($mode) && !empty($token)) {
            // Check the mode and token sent are correct
            if ($mode === "subscribe" && $token === $verify_token) {
                // Respond with 200 OK and challenge token from the request
                $http_code = 200;
                return $data = intval($challenge);
            } else {
                // Responds with '403 Forbidden' if verify tokens do not match
                $http_code = 403;
            }
        }
    }
    return $error;
}