UnauthorizedHandler
Handles an authentication failure for a typed authentication scheme.
The handler receives the current RoutingContext and the AuthenticationFailedCause for the failed authentication attempt.
The handler is expected to respond to the call, for example, with an error status or a redirect. If it completes without responding, the default challenge for the scheme runs, and the call is rejected with 401 Unauthorized when no challenge responds either; the route handler never runs for a failed authentication.