Add documentation for the new API endpoints

[jkuester]

In #9586 we added a number of new API endpoints that need to be documented on the docs page.

Honestly manually adding docs for the REST endpoints to that page is painful and the UX of trying to read the page are equally annoying. I know I have sworn to avoid any more feature creep in this project, but we really need to automate this via OpenAPI(#7005) and this might be a really good opportunity to do this.... 😅