Currently, the Koha REST API does not provide a way to link items to orders. This functionality would be useful for managing acquisitions and ensuring that items are correctly associated with their corresponding orders. Proposed Changes: 1) Allow specifying order_id when creating or updating items: POST /biblios/{biblio_id}/items: Support an optional order_id field to link the item to an order during creation. PUT /biblios/{biblio_id}/items/{item_id}: Allow updating an existing item to set or change its order_id. 2) Enable batch linking of items to orders: POST /acquisitions/orders/ and PUT /orders/{order_id} should accept an array of item IDs in the request body: {"items": [12345, 12346]} This would allow multiple items to be linked to an order in a single request. 3) Validation Requirement: Ensure that an item is not already linked to another order