toDataItem

Converts this ZkDocumentData instance to a CBOR DataItem representation.

The resulting DataItem will be a CBOR map containing:

• "id": The ZK system specification identifier as a text string

• "docType": The document type as a text string

• "timestamp": The timestamp as an ISO-8601 formatted string

• "issuerSignedItems": An array of issuer-signed data items

• "deviceSignedItems": An array of device-signed data items

• "msoX5chain": The X.509 certificate chain (only included if non-null)