Renders /federation/callback?code=&state=. It finishes the sign-in
(POST /api/federation/sessions) if this tab started it (startedHere),
and once: a code works only once, and a second request would fail the
sign-in. On success the user lands on /, signed in.
Return Type
React.JSX.Element
Usage
import { FederationCallback } from "src/pages/FederationCallback.tsx";