- Combine the /invite and /invitelink endpoints into one
- Return error messages from the backend
- Handle errors in the frontend
- Lower number of queries ran when calling the userinfo endpoint

Used to "log" a user out in the manual invite flow

To prevent hammering on the invite endpoint we throttle requests to the
endpoint to 100/day per ip.

Resolves: GREG-84

To prevent the invite id from showing up in various logs along the way,
we change to use an anchor in the invite url, and a post request to the
backend.

Invite links are now on the form /invitelink/#<uuid> and the frontend
redirects to /invite as usual after the session has been created.

Resolves: GREG-90

GREG-85: Adding some more data when Greg user profile is created. Doing some checks on fnr in invitation endpoint