Optionalentry: stringReadonlyreasonAn optional machine-readable reason, rendered into the response body alongside the message. DECLARED HERE rather than sniffed structurally at the mapper so the channel is part of the contract a subclass opts into, and so the mapper needs no import of any subclass to render it (see the header for why that import must not exist).
ReadonlystatusThe response status, 4xx or 5xx; any other status answers 500.
The refusal a fenced surface answers with: 503, because the deployment is deliberately not executing right now and will be again — an operator's condition, not the caller's mistake and not a code fault. Providers, schedulers, and clients that honour Retry-After semantics therefore redeliver rather than discard.