Add add-condition action to CONDITION_PENDING

[jakub-id]

No description provided.

[Copilot]

Pull request overview

Adds support for invoking the supplier-side add-condition action while a returnable Patron Request is already in CONDITION_PENDING, enabling suppliers to send additional conditions without leaving the state.

Changes:

• Added add-condition as an allowed action in the CONDITION_PENDING supplier state (self-transition on success).
• Updated the embedded returnables.json state model to match the YAML spec change.
• Extended ActionMapping tests to assert availability, listing, and transition behavior for add-condition in CONDITION_PENDING.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
misc/returnables.yaml	Adds add-condition action to supplier CONDITION_PENDING state with a self-transition.
broker/patron_request/service/statemodels/returnables.json	Mirrors the state model change in the embedded JSON used at runtime.
broker/patron_request/service/action_mapping_test.go	Updates/extends tests to cover the new action availability and transition in CONDITION_PENDING.