event_type'convert_error' | 'converted' | 'sending_error' | 'sent' | 'declined' | 'cancelled' | 'expired' | 'signed' | 'viewed' | 'downloaded' | 'signer_signed' | 'signer_email_bounced' | 'signer_viewed_email' | 'signer_viewed' | 'signer_forwarded' | 'signer_downloaded' | 'signrequest_received'
delivered_onstring date-time nullable
callback_status_codeinteger nullable
timestampstring date-time