OptionalsyncEarliest date to include in initial sync, based on the user's plan.
Non-calendar connectors should use this as their date filter (timeMin, created.gte, etc.) during initial sync. Calendar connectors should ignore this for API queries (to avoid missing recurring events) — the API layer filters non-recurring items automatically.
Undefined when no limit applies.
Context passed to onChannelEnabled with plan-based sync hints. Connectors can use these hints to limit initial sync scope.