Renders the page another gerbeur instance sends a user back to once they
let it sign them in here, /federation/callback.
f
FederationCallback(): React.JSX.Element
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.
Usage
import * as mod from "src/pages/FederationCallback.tsx";