Implement ICS sequence number for Google Calendar

[simonw]

https://support.google.com/calendar/thread/160470747/my-google-calendar-is-not-syncing-events-that-have-been-edited-in-my-ical-url?hl=en

Then, the actual event updates. Google calendar tracks calendar updates to make sure that no old updates will overwrite existing calendar contents. It uses the ics sequence field for that. An event in Google calendar only is updated if the sequence number in the downloaded ics file is higher than the last sequence number used.

https://icalendar.org/iCalendar-RFC-5545/3-8-7-4-sequence-number.html says:

 SEQUENCE:2

Need to figure out how to increment that correctly. Probably a count of records in the https://www.tidepoolstewards.com/admin/shifts/shiftchange/ for that team.

[simonw]

Relevant code: https://github.com/natbat/pillarpointstewards/blob/ec57fba4300979599b25cec36ad788bc1c4c7f15/pillarpointstewards/shifts/ics_utils.py#L52-L67

[simonw]

Also relevant:

• https://stackoverflow.com/questions/50422635/how-to-add-modify-events-in-google-calendar-with-ics-file

[simonw]

I should probably update my TIL too https://til.simonwillison.net/ics/google-calendar-ics-subscribe-link