I have implemented In-App Purchase in an old ASP.NET project. But the problem is if the subscription got expired or auto-renew somehow got failed. How am I supposed to update at the server end? I don't know what to use 'web hooks' or any 'cron job' or any other method for this so that the receipt verification also got updated at the server end. This is an old ASP.NET Web API project. I have an azure cloud subscription for this project. I do not want to use any third-party library.