Privacy of in-app purchases: how much user data does the app developer get?

When a you do an in-app purchase like buying a feature or subscription the the app and the developer is getting data on your purchase. I searched a bit the Google documentation but I wasn't able to determine what user-data from the used Google-account used by the purchase is made accessible to the app and it's developer. Technically it should be possible to implement this whole process in a way that the app and it's developer does not get access to any user-related data like Google account e-mail, user name or similar data. The app and it's developer should only get the data what item/subscription you have bought and may be a random user-id only Google can relate to your account. Is there any official documentation available about the privacy of in-app purchases like what user-related data is shared with the app and it's developer?