Update inventory PO item

Returns: Updated InventoryPOItem entity

Permission required: Manage Inventory

Note: This method may only be used to update the cost of inventory PO items that are not associated with a base inventory PO. To update the inventory levels for inventory PO items, use the Add inventory transaction method instead.

Deprecated 3/30/2023. Will be removed 10/1/2023. Cost may now be captured for each fulfillment step of each PO item. Set BaseCost via Add inventory PO item fulfillment or Update inventory PO item fulfillment instead.