I have a Flutter app with a Node backend, and I have users input promotional codes during signup. Later, when the user goes to pay for a subscription to my app, if they have entered a promotional code during signup, then I want to display the normal price with an X% discount.
On App Store Connect, I can add blanket promotional offers, or "one time codes", which requires the user to click a link, or enter a code on Apple's side. That part is extremely unclear to me, but I am sure it's not what I need.
Alternatively, I am thinking of making a new offering altogether and just offering that instead of my usual one, but this is a lot more work and is very error-prone. What's the best way of doing this?