Add /healthz endpoint to server (#259)

Co-authored-by: Michael Eischer <michael.eischer@fau.de>

mux.go

@@ -112,6 +112,9 @@ func NewHandler(server *Server) (http.Handler, error) {
 			mux.HandleFunc("/metrics", server.wrapMetricsAuth(promhttp.Handler().ServeHTTP))
 		}
 	}
+	mux.HandleFunc("/healthz", func(w http.ResponseWriter, _ *http.Request) {
+		w.WriteHeader(http.StatusNoContent)
+	})
 	mux.Handle("/", server)
 
 	var handler http.Handler = mux