Conectarme usando Goozle a un servidor externo a Drupal pasando variables JSON

<?php

namespace Drupal\suggestions_module\Controller;


use Drupal\Core\Ajax\AjaxResponse;
use Drupal\Core\Controller\ControllerBase;
use Drupal\Component\Serialization\Json;




/**
 * Class SuggestionsIbmController.
 *
 * @package Drupal\suggestions_ibm\Controller
 */
class SuggestionsIbmController extends ControllerBase {

  /**
   * {@inheritdoc}
   * @return array
   * @throws \Drupal\Component\Plugin\Exception\InvalidPluginDefinitionException
   * @throws \Drupal\Component\Plugin\Exception\PluginNotFoundException
   * @throws \Drupal\Core\Entity\EntityStorageException
   * @throws \GuzzleHttp\Exception\GuzzleException
   */
  public function showSuggestions() {


    /**
     * Descarga de Sugerencias y filtrado para enviarlas
     */
    // Load entities by their property values.
    $contenidos_for_suggestions = \Drupal::entityTypeManager()
      ->getStorage('node')
      ->loadByProperties(['type' => 'review']);


    foreach ($contenidos_for_suggestions as $contenido_for_suggestions) {

      $check_is_replied = $contenido_for_suggestions->get('field_replied')->value;

      if($check_is_replied == "No"){
        $check_id_contenido = $contenido_for_suggestions->get('nid')->value;
        //print "No tiene contenido: ".$check_id_contenido;

        /**
         * Configuring Json to server send
         */

        $json_array = [
          'data' => []
        ];

        $node_pre = \Drupal\node\Entity\Node::load($check_id_contenido);

        $json_array['data'][] = array(
          'type' => $node_pre->get('type')->target_id,
          'id' => $node_pre->get('nid')->value,
          'attributes' => array(
            'Campo_1_Name' => $node_pre->get('campo_1_name')->target_id,
            'Campo_2_Name' => $node_pre->get('campo_2_name')->value,
            'Titulo' => $node_pre->get('title')->value,
            'Campo_4_Name' => $node_pre->get('campo_4_name')->value,
          ),
        );


        $current_user = \Drupal::currentUser();
        $account = $current_user->getAccount();

        $username = $account->name;
        // pass would be hard to get as stored hashed
        //... so you would need to get a bit tricky to "catch" the users password when they log in...
        $pass = 'mi_PASS';
        $auth = 'Basic ' . base64_encode($username . ':' . $pass);
        $token = 'EL TOKEN OBTENIDO USANDO /session/token AL FINAL DE LA URL';

        // Logs a notice
        \Drupal::logger('mi_modulo_custom')->notice('ID Contenido enviado:'.$check_id_contenido);

        $client = \Drupal::httpClient();
        $response = $client->request(
          'POST',
          //'https://URL_SERVIDOR_EXTERNO',


          [
            'timeout' => 600,
            'json' => $json_array,
            'headers' => [
              'Authorization' => $auth,
              'Content-Type' => 'application/hal+json',
              'X-CSRF-Token' => $token,
            ],
          ]);

        $suggestions_options = Json::decode($response->getBody());
        $suggestions_options = $suggestions_options['VALOR_EXTERNO_RECIBIDO'];
        $items = [];

        foreach ($suggestions_options as $suggestion_option) {
          $items[] = $suggestion_option['proposal'];
        }
        $check_is_replied = $contenido_for_suggestions->get('nid')->value;

        //ksm($check_id_contenido);

        $node = \Drupal\node\Entity\Node::load($check_is_replied);

        $node->field_new_proposal = $items;

        $node->save();

      }else{
        $check_id_contenido = $contenido_for_suggestions->get('nid')->value;
       // print "Sí que tienen respuestas" .$check_id_contenido;
      }
    }


    return [
      '#type' => 'markup',
      '#markup' => $this->t('Carga realizada correctamente: '),
    ];
  }