Appstore approval - Redeeming third-party gift codes through app

We have been asked by our client to develop an application that would enable redeeming gift codes that unlock additional content. The Application itself would not provide a way to purchase those codes.

It would work something like this -

1) a customer shops for groceries

2) when reciving the receipt/bill at the check-out the customer recieves a gift code.

3) entering this code in app unlocks additional premium content inaccessible otherwise.

The question is if this app would be approved by Apple?

In our opinion this model falls into the following point in Ap开发者_JS百科ple’s App Store Review Guidelines

11.14 Apps can read or play approved content (specifically magazines, newspapers, books, audio, music, and video) that is subscribed to or purchased outside of the app, as long as there is no button or external link in the app to purchase the approved content. Apple will not receive any portion of the revenues for approved content that is subscribed to or purchased outside of the app

but on the other hand there's this point:

11.1 Apps that unlock or enable additional features or functionality with mechanisms other than the App Store will be rejected

Have any of you know of application using similar business model?

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We did something very similar for a major snack food company. The user entered EAN codes (the European equivalent of UPC codes) from the packaging to unlock different musical instruments from within the application. Apple did not reject the app and it is still for sale today.