title: When to call finishTransaction on SKPaymentQueue in Server Product Model?
body: <p>I'm a little confused on when exactly to call:</p>
  
  <p><code>[[SKPaymentQueue defaultQueue] finishTransaction:transaction];</code> in a 'Server Product Model': <a href="http://developer.apple.com/library/mac/documentation/NetworkingInternet/Conceptual/StoreKitGuide/Art/store_transactions.jpg" rel="nofollow">http://developer.apple.com/library/mac/documentation/NetworkingInternet/Conceptual/StoreKitGuide/Art/store_transactions.jpg</a></p>
  
  <p>Should it be called when my server returns me that receipt is valid and I can display paid content or should I call it immediately after I get back receipt (purchased or restore) from itunes ?</p>
  
  <p>Thanks</p>