Add deprecation warning for /device/token endpoint

Signed-off-by: m.nabokikh <maksim.nabokikh@flant.com>

server/deviceflowhandlers.go

@@ -152,6 +152,9 @@ func (s *Server) handleDeviceCode(w http.ResponseWriter, r *http.Request) {
 }
 
 func (s *Server) handleDeviceTokenGrant(w http.ResponseWriter, r *http.Request) {
+	s.logger.Warn(`Request to the deprecated "/device/token" endpoint was received.`)
+	s.logger.Warn(`The "/device/token" endpoint will be removed in a future release.`)
+
 	w.Header().Set("Content-Type", "application/json")
 	switch r.Method {
 	case http.MethodPost:

server/server.go

@@ -320,7 +320,7 @@ func newServer(ctx context.Context, c Config, rotationStrategy rotationStrategy)
 	handleFunc("/device", s.handleDeviceExchange)
 	handleFunc("/device/auth/verify_code", s.verifyUserCode)
 	handleFunc("/device/code", s.handleDeviceCode)
-	// TODO(nabokihms): deprecate and remove this endpoint, use /token instead
+	// TODO(nabokihms): "/device/token" endpoint is deprecated, consider using /token endpoint instead
 	handleFunc("/device/token", s.handleDeviceTokenGrant)
 	handleFunc(deviceCallbackURI, s.handleDeviceCallback)
 	r.HandleFunc(path.Join(issuerURL.Path, "/callback"), func(w http.ResponseWriter, r *http.Request) {