Add --send-updates flag to 'gog calendar update' command

[ejc3]

Summary

The gog calendar update command is missing the --send-updates flag that exists on gog calendar create.

Problem

When updating an event's time (e.g., rescheduling a meeting), attendees are not notified of the change because there's no way to specify sendUpdates=all.

Expected behavior

gog calendar update should support --send-updates=STRING with values: all, externalOnly, none (matching Google Calendar API).

Google Calendar API Reference

The Events: update endpoint supports the sendUpdates query parameter.

Workaround

Currently users must delete and recreate events to notify attendees, which is not ideal.

Example

gog calendar update primary <eventId> --from "2026-02-03T15:30:00" --send-updates all

Thank you!