Android Question Promo Code Detect

thank you very much for sharing your experience with this issue. yours is certainly an excellent solution that I will consider. if, however, I put myself on the side of the user who has just bought the app with his own money and I see a pop-up appear asking me for an additional code to activate special functions, surely I would not be happy. I would think they want to get more money out of me and I would close it all by asking for a refund. what I was looking for was a solution that was transparent for the user who buys and automatic for the user who uses a promo code. knowing if he used a promotional code to buy the app is the most logical solution. Maybe one of the Erel's tricks could be the solution.