Configuration is the same as before with oauth, except you had to allow “insecure apps” in google - at least I did not find another way
The most important in configuration:
caldavio:calendarName:url=https://apidata.googleusercontent.com/caldav/v2/calendar-id/events
caldavio:calendarName:oauth=true
# client_id for OAuth
caldavio:calendarName:username=client-id-for-oauth
# client_secret for OAuth
caldavio:calendarName:password=client-secret-for-oauth