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/5xx only — see doErrorResponse.
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.