I'm building an iOS app and would like to add and in-app-purchase programmatically from our custom CMS/Web-app.
I can't seem to find any reference a (JSON or alternative) API where I can push relevant data to iTunes Connect to create an in-app-purchase remotely.
Sorry, for the rubbish question. I have hunted for answers and can't seem to find anything. Does anyone know what options I have here?
There are no official APIs for iTunes Connect or the Apple Developer Center. Either have a look at Fastlane/Spaceship (Official/Open Source) or the iTMSTransporter (Apple/XML).
Spaceship recently added the management of IAPs. With iTMSTransporter you can upload IAPs within the XML package of apps.