How to setup Google calendar sync
We use the standards offered by Google to authorise our app with their services and they are based on the OAuth2.0 Client.
Navigate to google cloud console
Create a newly registered app as a web app.
Your web origin should be: http://your.external.IP:8080 or without the port, if your server runs on port 80
Your redirect URI should be: http://your.external.IP:8080/RanFab/req.awggl2
Click Generate and copy and paste the Client ID and Client Secret Key into the Google section of your System Settings.
Now you should navigate to your RanFab external address and be able to sync your calendars once you authorise the process with Google.