As some of you brought up, we are lacking some documentation for the important changes for app developers. So I proposed to do this like the Laravel project and list the changes in every major release in prose.
This page is live now at https://docs.nextcloud.com/server/latest/developer_manual/app/upgrade-guide.html. I hope this makes developing and maintaining an app a bit easier. But please let me know if you have any feedback. I’m all ears hearing if we can improve anything about the format