Recaptcha is a special snowflake because it dynamically loads the script
and THEN renders with info from the registration request. This means we
need a back-channel for the UI component to 'tell' the stage that everything
is loaded. This Just Works which is nice.
- ServerConfig seems too specific to Vector, but we can always add it back later.
- Signup.js contains all the logic for determining what to show which was
previously in UI components.