Adding app purchase receipt handling in Qt

Hi,
Qt app (developed with Qt Purchasing API usage) was rejected from Mac OS X AppStore with following explanation:

"This app still does not check for the existence of a purchase receipt,which can prevent In-App Purchases from being correctly processed.

In-App Purchases will fail for users on Mac OS X 10.6 through 10.8 unless receipt validation is implemented on launch.

We recommend implementing receipt validation to resolve this issue. At a minimum, the app will need to check for the existence of an App Store receipt
and exit at launch with a status of 173 if it does not exist. See Validating Mac App Store Receipts for more information. "

Mac AppStore QA team is checking app for purchase receipt file and behavior of app, if that file with receipt is out of app bundle. If app was purchased from Mac App Store - it will contain receipt file in app bundle (someway of protecting distributing apps).

So right now in Qt Purchasing API we don't have any methods/funcs to handle that receipt. That is the reason why app could be rejected from Mac App Store - developer belives that all needed actions with purchases are implemented in Qt Purchasing API.

Here is the list of actions which QA Mac AppStore team is using to validate receipt in app - https://developer.apple.com/library/ios/releasenotes/General/ValidateAppStoreReceipt/Chapters/ValidateLocally.html#//apple_ref/doc/uid/TP40010573-CH1-SW6

Sure, those actions could be manually implemented by developer, but if we are saying that Qt Purchasing API supports iOS, Android and Mac AppStore - we need to provide more easier way for developer to handle it.

FYI: the same app successfully passed verification in iOS AppStore due different mechanism of receipt validation.