- Added quantity tracking fields (processedQuantity, processableQuantity, unprocessedQuantity) to ExchangeLineItem and ReturnLineItem objects.
- Introduced return timestamp fields (closedAt, createdAt, requestApprovedAt) and ReverseFulfillmentOrderDisposition.createdAt for better return lifecycle visibility.
- Deprecated ExchangeLineItem.lineItem; use ExchangeLineItem.lineItems instead, which may return multiple associated line items (breaking change).