Create one or more schedule / time-off / claim requests. Body is {items: [RequestIn, ...]} like POST /approve; a single RequestIn object is also accepted. Each item is RequestItem-shaped: type, person_id, requested_entries. resource_id is required for modify_ and cancel_. Optional decision defaults to approved so validation may leave it pending; pass pending to keep it pending. Returns 409 if that resource already has a pending request. Items and requested_entries for the same person whose windows fall in the same work week (that person's weekday_start) are submitted together so weekly rules apply to the full week, then returned 1:1 with the input items. Pass validate_only=true to run the same checks without writing.