PaymentController uses the "return_context" field instead of "transaction_id"

[roadster31]

Instead of using the "transaction_id" field for retrieving the Order, the PaymentController now uses the "return_context" field, which is initialized in the payment request with the order reference.

This is a safe way to remove filtering by module ID when searching the paid order :

$order = OrderQuery::create()
    ->filterByTransactionRef($result['transaction_id'])
    ->filterByPaymentModuleId($atos->getModuleModel()->getId())
     ->findOne();

We have now :

$order = OrderQuery::create()->findOneByRef($result['return_context']);

This way, modules extending Atos (such as AtosNx) are naturally supported the Atos PaymentController.

The PR also include minor code style fixes