message: CR: Handle loginErr
  Document errors: loginErr will not be possible with a no-op serialize
  Add TODO for /login redirect
diff: @@ -96,9 +96,11 @@ function createOnCallback(domain: string): express.Handler {
  return (req, res, next) => {
  passport.authenticate(`auth0-${domain}`, (err, user, _info, _extra) => {
  if (err) { return next(err); }
  + // TODO: redirecting to /login, a misconfiguration causes a confusing redirect loop
  if (!user) { return res.redirect('/login'); }
  req.logIn(user, (loginErr) => {
  - if (err) { return next(loginErr); }
  + // loginErr usually indicates a failure to serialize when using a session store
  + if (loginErr) { return next(loginErr); }
  res.redirect(req.session?.returnTo || '/');
  delete req.session?.returnTo;
  });
  