createDocument abstract method
Create a custom entity document with specified parameters.
Builds a Document from explicit components (type, data, signature) for extended entity information.
docType is the document type (e.g., "visa", "bulletin").
data is the optional raw data content of the document.
signature is the optional cryptographic signature for document verification.
Returns a new Document instance.
Implementation
Document createDocument(String docType, {
String? data,
TransportableData? signature
});