OPDC API error code

PERIOD_CLOSED

HTTP status 422

The target period is beyond the ledger's current period, or outside the postable window. 422.

The API answers with a problem document (RFC 9457) whose type is https://twinn.engineering/errors/period-closed, and with X-Error-Code: PERIOD_CLOSED. Branch on the code, never on the detail text.

How errors work, and what to retryEvery error code