Wrap System API Error as Problem Details Response

When a downstream System API call fails, the raw Mule error must never reach the API consumer unprocessed. This challenge places you inside an on-error-continue handler where you transform a Mule error object into a standardized Problem Details response. The upstream Inventory API is not always reachable — some failures return a structured HTTP error body, others return nothing at all — so you must guard every conditionally present field before the response goes out.