Returns per-entity calendar intervals between startDate and endDate (weekly patterns,
stored blocks, appointments, recurring rules, holidays). At least one of LocationIds,
ResourceIds, or ServiceId must be provided. Scope IDs only match entities owned by
the authenticated company.

Use syncExternal=true to ingest connected Google or Outlook busy events before listing.
Ingest runs only for Resources owned by the authenticated company, including when
ResourceIds is supplied. This flag triggers just-in-time External Calendar ingest
only; it does not hide stored external blocks when false. That differs from
GET /v3/availability, where syncExternal=false intentionally bypasses external busy
when calculating bookable slots. Adds latency; keep date ranges narrow.