Inventory transfer webhooks include origin and destination location IDs, and mutation documentation clarified

Shopify's Admin GraphQL API (2026-04 version) now includes origin and destination location IDs as Global IDs in inventory transfer webhook payloads, eliminating the need for extra API calls to determine transfer locations. The fields are omitted (not null) for older API versions or non-location transfers. Additionally, documentation for inventoryTransferSetItems and inventoryTransferRemoveItems mutations has been clarified to better describe upsert behavior, quantity handling on different transfer statuses, and no-op handling. Several error messages have also been made more descriptive, though error codes remain unchanged.