We have several payment types that you'll see during the purchase flow: Promotion, Gift Card/Coupon, Groupon, Class Pass, Comp, Pay Later, etc. Choosing these other payment types/funding sources allows you to add notes (just like cash, etc) to the purchase so you can add code, coupon number, Groupon purchase number, anything you'd like! Also, you can then search/sort in your Sales Report by the same payment types/funding sources.
These other payment types/funding sources, like Groupon, Pay Later, Class Pass, etc, don't have any integration with those services - but you can use the notes field during the purchase process to track any codes, etc.
If there's a payment type we missed that you'd like to see, let us know!