After setting up things with Google's OAuth2 implementation I get a token and refresh token.
Starting the app after setting the refresh token from the last run should allow to start a new session without going through the OAuth2 flow again.
Instead I get:
qt.networkauth.replyhandler: Error transferring https://oauth2.googleapis.com/token - server replied: Bad Request
This is due to NetworkAuth not setting the client id and shared secret.