Client-side per-app access rights

[Grunthos]

Problem

I'd like to grant various apps access to apps on my NC server, but not to the whole server.

For example, grant a calendar app on my phone access to CalDav, or Floccus access to the Bookmarks app. I do not want them to be able to do anything other than run Calendar or Bookmarks on my behalf. If someone hacked the app on my phone, I do not want those credentials to grant access to Files etc.

Describe the solution you'd like

Auth keys (OAuth?) on a per-app basis.

Describe alternatives you've considered

A really low-tech solution is to create one account per special app, but it is pretty unsatisfactory in terms of integration!

[kesselb]

Duplicate of #9117