OptionalartifactOptional Artifact reference recorded against the (first) document for provenance.
OptionalartifactDocuments to sign. The caller resolves bytes (e.g. from an Artifact Version).
OptionalentityPolymorphic originating record (entity half).
OptionalmessageOptionalmetadataProvider custom fields.
OptionalproviderSigners.
OptionalrecordPolymorphic originating record (record half).
Optionalsendtrue → send immediately; false → create as draft. Defaults to true.
Account (provider instance) to send through.
Envelope title / email subject.
Input for SignatureEngine.SendForSignature.