Pending (requires CancelPending) or DeadLettered → Discarded immediately. InFlight (requires CancelInFlight) → CancelRequestedAt set, CancelRequested: true (spec 03 §7).
CancelRequested: true
condition null = all non-Idle keys. Returns null when !ListPartitions.
Pending (requires CancelPending) or DeadLettered → Discarded immediately. InFlight (requires CancelInFlight) → CancelRequestedAt set,
CancelRequested: true(spec 03 §7).