My client wants to turn a paid Android app into a free one with subscription options for premium features.
However users that have paid for in the past should not need to subscribe for premium features.
How can I technically check if a users has bought the app once it is free? Does the Google License Verification Library still provide a license even the app has been turned into a free one?
I learned that it's possible to see the purchase history for in-app/subscription billings but for a onetime paid app, the billing library does not track it.
Any help is appreciated :)
I checked the Google billing library and searched for examples but it does not provide any good answer.