Cancelling a subscription inside an app?

There is now API for showing an Apple-managed UI on your UIWindowScene for managing subscriptions (https://developer.apple.com/documentation/storekit/appstore/3803198-showmanagesubscriptions) but I don't think you can display your own UI for cancelling or programmatically cancel without interaction.

StoreKit2 has added a new function - showManageSubscriptions to display a manage subscription sheet within the app that’s the same as what customers can view in their account settings in the App Store app, or by choosing Settings > Apple ID > Subscriptions on an iOS or iPadOS device. The sheet displays the customer’s currently active subscription for your app and the options to view, upgrade, downgrade, or cancel their subscription.