Transfer domain and subscriptions to another Google reseller

1. TransferDomainsController.php

<?php

namespace App\Http\Controllers\Customer\Contact\GoogleWorkspace;

use App\Http\Controllers\Controller;
use App\Http\Requests\Customer\GoogleWorkspace\Transfers\TransferSubscriptionsRequest;
use App\Models\Contact;
use App\Services\GoogleSubscriptionService;
use Google\Service\Exception;

class TransferDomainsController extends Controller
{
    /**
     * Show list of transferable subscriptions.
     *
     * @param TransferSubscriptionsRequest $request
     * @param Contact $contact
     * @param string $domain
     * @param string $token  Encrypted token value.
     * @return void
     */
    public function transferSubscriptions(TransferSubscriptionsRequest $request, Contact $contact, string $domain, string $token)
    {
        // Fetch subscription details.
        $hasException = false;
        $google = new GoogleSubscriptionService();
        $subscriptions = $google->getSubscriptionsByDomain($domain, decrypt($token));

        // Transfer subscriptions.
        // This is where it breaks, continue with GoogleSubscriptionService.php.
        $response = $google->transferSubscriptions($domain, $subscriptions, decrypt($token));

        // ....
    }
}

2. GoogleSubscriptionService.php

<?php

use Google\Service\Reseller;
use Throwable;

class GoogleSubscriptionService
{
    private $client;

    public function __construct()
    {
        $this->setupClient();
    }
    
    /**
     * Setup Google Client
     *
     * @return void
     */
    private function setupClient()
    {
        $google_client = new Client();
        $google_client->setApplicationName('App Name');
        putenv('GOOGLE_APPLICATION_CREDENTIALS='.base_path().'/google_client.json');
        $google_client->useApplicationDefaultCredentials();
        $google_client->setScopes([Reseller::APPS_ORDER]);
        $google_client->setSubject('user@domain.com');

        $this->client = $google_client;
    }
    
    /**
     * Get subscriptions by domain
     *
     * @param string $domain
     * @param string $token
     */
    public function getSubscriptionsByDomain($domain, $token)
    {
        try {
            $google = new Reseller($this->client);
            $data = $google->subscriptions->listSubscriptions([
                'customerId' => $domain,
                'customerAuthToken' => $token,
            ])->getSubscriptions();

            return $data;
        } catch (Throwable $e) {
            return $e;
        }
    }
    
    /**
     * Transfer subscriptions via a batch request.
     *
     * @param string $domain
     * @param array $subscriptions
     * @param string $token
     */
    public function transferSubscriptions(string $domain, array $subscriptions, string $token)
    {
        // Make sure to activate batch requests.
        $this->client->setUseBatch(true);

        try {
            $google = new Reseller($this->client);
            $batch = $google->createBatch();

            // Iterate subscriptions and add request to batch.
            foreach ($subscriptions as $subscription) {
                // Build request.
                $request = $google->subscriptions->insert($domain, $subscription, [
                    'customerAuthToken' => $token,
                ]);

                // Add request to batch.
                $batch->add($request);
            }

            // Execute batch.
            return $batch->execute();
        } catch (Throwable $e) {
            return $e;
        }
    }
}

3. request-data.php

// Request data as generated by the PHP Google API library
// Google\Http\Batch, logged this info on rule 131

array:4 [▼
  "method" => "POST"
  "url" => "https://reseller.googleapis.com/batch"
  "headers" => array:2 [▼
    "Content-Type" => "multipart/mixed; boundary=904299535"
    "Content-Length" => "1006"
  ]
  "body" => """
    --904299535
    Content-Type: application/http
    Content-Transfer-Encoding: binary
    MIME-Version: 1.0
    Content-ID: 1492737493
    
    POST /apps/reseller/v1/customers/######/subscriptions?customerAuthToken=####### HTTP/1.1
    Host:reseller.googleapis.com
    content-type:application/json
    X-Php-Expected-Class:Google\Service\Reseller\Subscription
    
    {"billingMethod":"ONLINE","creationTime":"1661351293638","customerDomain":"######","customerId":"######","kind":"reseller#subscription","resourceUiUrl":"https:\/\/admin.google.com\/ac\/billing\/subscriptions?ecid=######","skuId":"1010020027","skuName":"Google Workspace Business Starter","status":"ACTIVE","subscriptionId":"4321824362","seats":{"kind":"subscriptions#seats","licensedNumberOfSeats":1,"maximumNumberOfSeats":1},"plan":{"isCommitmentPlan":false,"planName":"TRIAL"},"trialSettings":{"isInTrial":true,"trialEndTime":"1663943293625"},"transferInfo":{"minimumTransferableSeats":1,"transferabilityExpirationTime":"1662560942807"}}
    
    --904299535--
    """
]

response-data.php

array:1 [▼
  "response-1492737493" => Google\Service\Exception {#1779 ▼
    #message: """
      {
        "error": {
          "code": 400,
          "message": "Licensed number of seats field is read-only",
          "errors": [
            {
              "message": "Licensed number of seats field is read-only",
              "domain": "global",
              "reason": "invalid"
            }
          ]
        }
      }
      """
    #code: 400
    #file: "/Users/#####/Desktop/Development/app/vendor/google/apiclient/src/Http/REST.php"
    #line: 130
    #errors: array:1 [▼
      0 => array:3 [▼
        "message" => "Licensed number of seats field is read-only"
        "domain" => "global"
        "reason" => "invalid"
      ]
    ]
    trace: {▼
      /Users/######/Desktop/Development/app/vendor/google/apiclient/src/Http/REST.php:130 {▼
        Google\Http\REST::decodeHttpResponse(ResponseInterface $response, RequestInterface $request = null, $expectedClass = null) …
        ›     // Check if we received errors, and add those to the Exception for convenience
        ›     throw new GoogleServiceException($body, $code, null, self::getResponseErrors($body));
        › }
      }
      ...      
    }
  }
]