CROSSLINK-213 Add items endpoint and populate items on SAM message

[JanisSaldabols]

No description provided.

[Copilot]

Pull request overview

This PR adds first-class support for patron-request “items” by encoding/decoding item lists in ISO18626 SAM notes, persisting items on incoming Loaned messages, and exposing a new API endpoint to retrieve items for a patron request.

Changes:

• Add /patron_requests/{id}/items API endpoint and OpenAPI schema for PrItem.
• Add shared parsing/escaping helpers and shim logic to move item identifiers between DeliveryInfo.ItemId and MessageInfo.Note.
• Persist parsed items when handling incoming SupplyingAgencyMessage with status Loaned, and update related tests/repo methods.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
broker/patron_request/api/api-handler.go	Adds items endpoint, refactors PR lookup helper to write HTTP errors directly, maps DB items to API model
broker/oapi/open-api.yaml	Adds PrItem schema and /patron_requests/{id}/items path
broker/common/common.go	Introduces #MultipleItems# encoding helpers for packing/unpacking items in notes
broker/shim/shim.go	Adds Alma/ReShare logic to unify items into notes on incoming messages and set ItemId on outgoing messages
broker/patron_request/service/message-handler.go	Saves parsed items on Loaned SAM messages
broker/shim/shim_test.go	Adds shim round-trip tests for item encoding/decoding
broker/patron_request/service/message-handler_test.go	Adds tests for saving items and updates Loaned SAM test to include item block
broker/patron_request/db/prrepo.go	Renames repo method to GetItemsByPrId
broker/test/patron_request/api/api-handler_test.go	Exercises new /items endpoint in an end-to-end test
broker/test/patron_request/db/prrepo_test.go	Updates repo test to new method name
broker/patron_request/service/action_test.go	Extends mock repo to capture saved items

[jakub-id]

@JanisSaldabols see Copilot comments