Retrieve an operation

Creates an asynchronous batch operation. All items in the batch are processed with the same operation `type`, which also determines the structure of each item's `payload`. The operation is accepted with a `Location` header pointing to it and processed asynchronously. Poll the retrieve operation to track its progress. In addition to `operations.manage`, the credential must have the permission required by the selected operation type. Repeating the request with the same `Idempotency-Key` returns the same operation instead of creating a new one. The request is rejected with `operation_type_unknown` for an unsupported type, `duplicate_item_key` when item keys are not unique, `too_many_items` when the batch exceeds the maximum number of items for the type, and `operation_backlog_exceeded` when the account has too many unfinished operations.