Ingest leads from a webhook

Public webhook ingest endpoint. Authenticate with the bearer token returned by the connect call (Authorization: Bearer <token>). The request body must contain a leads array of up to 500 records per call. Returns 202 with counts of received, created, duplicate, and skipped leads.

Error codes: CLAY_CONNECTOR_NOT_FOUND (404), CLAY_CONNECTOR_DISCONNECTED (403), CLAY_CONNECTOR_TOKEN_REQUIRED (401), CLAY_CONNECTOR_TOKEN_INVALID (401), CLAY_EMPTY_PAYLOAD (422), CLAY_BATCH_TOO_LARGE (422).