Changes to Create Artifact

added the new optional request property source_format

added the optional property anyOf[subschema #1: SessionResponse]/last_content_updated_at to the response with the 200 status

added the optional property anyOf[subschema #2: DocumentResponse]/last_content_updated_at to the response with the 200 status

added the optional property anyOf[subschema #3: ArtifactListItem]/last_content_updated_at to the response with the 200 status