Hi, I am new at adding in-app purchases / subscriptions to my app. I am making a fitness app, where users can join multiple challenges. apple is not letting us implement 3rd party payment system for users to join challenge, so i need to do IAP in my app. I am bit confused which one i choose, In app, a user can join a challenge for specific time (i.e. 30 days, 1 week, 2 week) period the time is depending on a challenge which is created by nutritionists, but a user can also join another challenge at a time. lets say for example, there are 2 challenges available right now 30 days daily workout challenge 30 days weight loss diet challenge both challenges have the same price. I have made in app purchase called 'challenge 13.99' (product price in IAP is 13.99 USD). whenever user jones the 1st challenge they buy for productID 'challenge 13.99'. now I want to join 2nd challenge as well, so now will i get something like 'user already subscribe to this product' from the apple server or let me buy same product again?