Would my app get rejected if I were to just send users to the web page for subscription management?
Most likely, because there you are providing them with mechanisms to pay for your content without using Apple's purchasing mechanism. If you think about the problem the other way - if it would be that easy to bypass Apple's purchasing mechanism, everyone would be doing it, especially big companies.
My question is, do I need to implement this subscription in my app as an in-app purchase?
I'm pretty sure this is the only option in this case.
Topic:
App & System Services
SubTopic:
StoreKit
Tags: