Third party payment provider in app for API data

After reading several threads on Stackoverflow / Reddit it’s still quite confusing what is allowed on Android / iOS regarding payments.

I have a an app available for iOS and Android and a web app dashboard (plain PHP / MySQL, will become a Ionic Dashboard). The iOS / Android / Web app uses an API where your profile and game statistics are stored. To cover the costs of the server I want to add a premium membership feature. Users can subscribe on a monthly / yearly base. This allows the user to get more statistics available in the app (iOS, Android and Web app).

The idea is the same as Spotify (free account / paid account) with the difference that you get music without ads with Spotify and with this app you will get access to more statistics data / more filter options in the API.
But is it allowed ? Because you get extra data in the app (so you would think In App Purchases), however it can be consumed in the web app so Stripe / Mollie intergration would be allowed)