I'm developing an app which has in-app-purchases with Subscriptions (the user can buy a monthly/yearly subscription). How do I get my back-end get notified about subscription-related actions (new/cancelled/renewed/etc)?
I did find how to do it with Google PlayStore:
https://developer.android.com/google/play/billing/billing_subscriptions.html#realtime-notifications
The In-app Billing API provides server push notifications that give developers the capability to monitor state changes for Play-managed subscriptions. To enable this capability, you will need to integrate your backend with Cloud Pub/Sub using your own Google Cloud Platform (GCP) project, and fill in Google Play Console the Pub/Sub topic to which Play should publish notifications.