title: How to store in-app purchases for offline availability on per-user basis
body: <p>It seems that keychain on iOS stores data on a per-app basis rather than per-user.</p>
  
  <p>So if I store information about in-app purchases in the keychain, these products will remain available on the device regardless of which Apple-id is currently logged in.</p>
  
  <p>I could require network-access and perform a restore to know which products should be available, but it seems to be bad practise to do a non user-initiated retore. Also, the app should function properly offline.</p>
  
  <p>My question is: How do I protect in-app purchases from being available to users other than the Apple-id that bought them?</p>