Change Details

Part of [ENG-5153](https://linear.app/comm/issue/ENG-5153) Depends on D9398 Now we can start using the new `/webapp/` and `/keyserver` urls in other places.

Part of [ENG-5153](https://linear.app/comm/issue/ENG-5153) Depends on D9398 Now we can start using the new `/webapp/` and `/keyserver` urls in other places. This also brings back the option of testing the web app with "staging" keyserver because it sets the `urlPrefix` to the one specified in the url facts (passed as a variable in html) (more context in D9145).

Part of [ENG-5153](https://linear.app/comm/issue/ENG-5153) Depends on D9398 Now we can start using the new `/webapp/` and `/keyserver` urls in other places. This also brings back the option of testing the web app with "staging" keyserver because it sets the `urlPrefix` to the one specified in the url facts (passed as a variable in html) (more context in D9145).