Register/remove an API key with the web interface

As a simple user of debusine.debian.org, I want to be able to use the "debusine" CLI to experiment. Since I don't have admin rights on the server and can't run "debusine-admin create-token", I need to be able to generate an API key tied to my user through the web interface.

I also need to be able to remove any API key that is no longer relevant.