I'm looking to implement a document repository (not to the extend of XDS). We could always roll our own service interface but are looking to instead leverage either the DocumentManifest or DocumentReference resource implemented in FHIR REST services using ASP.NET.
One thing we need to capture though is the identity of the submitter (a person). This service is called from other software that would handle authentication of users. We need a way for those applications to pass the identity of the submitting user to the rest service. That identity isn't modelled in the DocumentManifest or DocumentReference resources because the user uploading the document isn't an attribute of the document, it's metadata about the transaction.
Any suggestions on how we should best go about doing this? Should we use an extension, resource metadata or other approach?