Add auth logic for stomp clients over ws

This MR checks STOMP CONNECT frames for the jwt. A user connecting to STOMP will have to send the jwt as the header token to the backend which authenticates it and caches the jwt for the underlying (stomp-)session-id. Furthermore, when there is a header ars-user-id, the backend checks if the user sending the request has authenticated himself and the given ars-user-id is the same as the one stored in the jwt.