Is it possible to generate promo codes for in app purchases? I have a free app with one in app purchase option, and I'd like to offer that IAP for free to some helpful users. In iTunes Connect it appears I can generate promo codes but those codes appear to be for the app itself (which, again, is free so I don't get it.)

Google searching brings up all sorts of claims that Apple doesn't allow you to create promo codes for in app purchases, but those threads are a couple of years old now. Can promo codes be created for IAP or is it just for apps themselves?
It's possible since October 28, 2016, see Apple's guide.