Workflow record callback

The events OpenRelay POSTs to a workflow record's callback, and the answers it accepts: the next requests to run, a pause, or the outcome. A workflow record is a batch record whose body carries openrelay.workflow. OpenRelay POSTs an event to its workflow.url, runs the requests the answer returns, and POSTs their results as the next event, until the callback answers completed or failed. The URL is the record's own, not a registered webhook. The request carries the record's workflow.authorization value verbatim as its Authorization header, and Content-Type application/json; it is not signed. Each event is delivered up to four times, with pauses of 1, 2 and 3 seconds between attempts and each attempt bounded by callback_timeout_ms. A timeout, a connection error, a 429 or a 5xx answer is retried, and so is a redirect, which is never followed. When all four attempts fail, the record fails with workflow_callback_unreachable and the rest of the batch keeps running. Any other non-2xx answer fails the record with workflow_callback_rejected.

{  "event_id": "wf_evt_8b2e4f6a1c3d5e7f9a0b2c4d6e8f0a1b",  "event": "results",  "workflow_id": "batch_9f8e7d6c5b4a:contract-42",  "record_id": "contract-42",  "step": 1,  "attempt": 2,  "context": {    "contractId": "contract-42"  },  "results": [    {      "id": "payment",      "stage_id": "payment",      "attempt": 1,      "custom_id": "payment",      "status_code": 200,      "body": {        "choices": [          {            "message": {              "content": "Net 30."            }          }        ]      },      "usage": {        "input_tokens": 11820,        "output_tokens": 140      }    }  ]}