InAppPurchase needed. (!READ DESCRIPTION)

Shortly: Just make HTTP request with retrofit to play market and handle response: OK -> remove stub activity / Error -> Activate stub activity. Detailed below: 1) Please check the existing logic that I attached as a file. (Just copy it to new class in Studio). Now it calls the Play Market and call subscriptions I have there. I have created and set up subscriptions on Play Market. 2) I need to have: - 1 type subscription with regular monthly payment (for example 5$ per month) - 2 type subscription with 3 months payments (for example 15$ charge for 3 months) 3) Set up 1 free month trial before it starts charges 4) After 1st subscription done need to save details in the firebase. Save date that is +1 month of the current date in the database. So the app will make a call to the play market only after 30 days. 5) Create activity stub that suppose to block app if subscription is not active. Handle the positive and negative scenarios: - Positive - Subscription is active - open payed features - Negative - Subscription is inactive - close payed features 6) Need to handle all errors that might happen while user subscribing by showing proper dialog window with proper message as a description P.S. For now Back end verification is in process so while testing you will call Play Market directly from the device. After that I will make it through the back end (you don't need to worry about that. I am the developer so I will provide detailed description how it suppose to work.