How do I configure a usable synchronisation with Google calendar

Question

I think I have tried every permutation of configuration to synchronise Lightning with Google calendar.
I have Thunderbird 31.1.2 and Lightning 3.3.1
The GDATA provider has the well documented issue of either re-mailing all meeting attendees, or not sending out invitations to meetings, so this doesn't really work for me.
I have succeeded in seeing my Google calendar by using the iCalendar(ICS) option, but whenever I add a new calendar event in Lightning I get a "An error occurred when writing to the calendar 'My Name'!
Error Code : MODIFICATION_FAILED
When I try using CalDAV I don't see the events in my Google calendar in the resulting calendar in Lightning. I'm not sure I have the right 'Location' parameter, I have multiple Google calendars, the details available on the various web forums are not very explicit about how to get the location when using multiple Google calendars.
Finally the Post on the Mozilla support forum states that I should use the Google Calendar option, which is not present!
I am sure this is possible, any help would be appreciated.
I have now turned on full logging and see the error:
[JavaScript Error: "[calCachedCalendar] replay action failed: null, uri=https://www.google.com/calendar/dav/{myusername}%40gmail.com/events, result=2147500037, op=[xpconnect wrapped calIOperation]"]
I think I have solved this one already. Deatails of the correct CalDAV locations can be found here:
https://blog.mozilla.org/calendar/2013/09/google-is-changing-the-location-url-of-their-caldav-calendars/
and here:
https://developers.google.com/google-apps/calendar/caldav/v2/guide#connecting_to_googles_caldav_server
It would be useful to update the Mozilla documentation accordingly. Can I help do that?

Answer 1

Caldav works for me.
I set it according to what is described here:
https://blog.mozilla.org/calendar/2013/09/google-is-changing-the-location-url-of-their-caldav-calendars/
Lightning doesn't let me edit a calendar's address once it's been inserted. I have to delete the existing calendar and then add it again.
What documentation have you found to edit? It seems to me that for years it has relied on a page at google, and that disappeared when they stopped referring to the now defunct stand-alone calendar, Sunbird. I'm not sure there's ever been an authoritative reference owned by Mozilla. Those documents referring to endpoints aren't easy to find.