Hello. We have the same problem described in original question, but slightly different in that the issue for us is when a user subscribes by redeeming an offer code. For subs they purchase directly from our mobile app, we know the user's id at time of purchase, create the association between the user and the new subscription transaction id and then use those identifiers we receive in app store notifications to update the subscription status for the user (essentially just as Oscar described). However, if a user redeems a code for a free subscription via redemption url or by entering the code directly in the app store, bypassing our app, we receive an Notification of Type: OFFER_REDEEMED directly from app store and we don't have a transaction yet on our backend to know which user just subscribed to a new subscription using the redemption code. Any suggestions/ideas/info on handling that variation is very much appreciated!

Same question with v2 notifications. When a user redeems an offer code outside of our app, we need some way to tie it to a user on our backend side. Please share any solutions you may have come across. Thanks

Same question here. The only 'solution' I have seen others suggest is to create new groups and new IAPs (with new unique IDs) for our subscriptions under whatever group. That's not a solution. We want to move existing IAPs to a new group keeping their current IDs. Thanks