My app was rejected because according to Apple:
> We understand that you've provided both premium and non-premium testing accounts. Regarding 3.1.1, since the app allows users to purchase premium plan using payment mechanisms other than In-App Purchase, it isn't in compliant with the 3.1.1 Guidelines.
> To resolve the issue, it would be appropriate to add the ability to pay for them in the app, using In-App Purchase.
With my app currently, the user installs it and can use it for free, however it has premium features, which you unlock by subscribing to a monthly subscription. You do this by having an account on the app, and pressing a "subscribe" button, which then on the following page opens your browser with a Stripe payment link. You complete the checkout, and go back to the app, which registers from the backend that you have gone premium.
So I'm just trying to understand, because their comment on the rejection isn't very informative and I'm new to this: Does my app HAS to have Apple's In-App purchasing and checkout implementation, no matter what? Or can I do it with having for example a direct link or button leading to a checkout page from Stripe, or a WebView that is still inside the app, or any other way of doing it?
By the way I'm not native English.
Thanks in advance!