at property
At is when it was published, RFC 3339, on the server clock. You do not supply it: a record whose date the audited party chose is not a record.
Please note: This property should have been non-nullable! Since the specification file does not include a default value (using the "default:" property), however, the generated source code must fall back to having a nullable type. Consider adding a "default:" property in the specification file to hide this note.
Implementation
String? at;