iOS mobile application : Apple offer codes

We have an application in production.

For iOS, we use Apple payment system but we have a problem with Apple offer codes (https://developer.apple.com/documentation/storekit/original_api_for_in-app_purchase/subscriptions_and_offers/implementing_offer_codes_in_your_app).

When an user use an offer code with Apple, we don't know how to get the response from Apple if the payment it's ok or not.

Someone to help us for this part ?

Best regards,
Roger