Configuring CloudKit CKModifyRecordsOperation retries to prevent duplicate writes
Goal Configure a CloudKit modify operation so that a retry after a timeout or rate‑limited error does not create a duplicate record and does not silently overwrite concurrent edits made by another client. Constraints and uncertainty The operation uses a fixed CKRecord.ID to guarantee idempotency, but the chosen savePolicy (.ifServerRecordUnchanged, .changedK