How do you process subscription renewals from RevenueCat?

Hi community,

How do you pas Firebase/Firestore user id to RevenueCat with the first purchase? How do you know for which user your Firebase just got webhook (subscription renewal) from RevenueCat?

Should we use some custom actions after login, purchase to pass Firestore user id to RevenueCat? Or maybe should we use Firebase RevenueCat extension?
Or because of FF integration with Firebase and RevenueCat, webhook from RevenueCat already includes user id from Firestore?

What's the best practice for FlutterFlow developers?

Thanks.