Implement IHE MHD ITI-65 Provide Document Bundle to submit clinical documents via FHIR

Verified steps

1. Construct a FHIR transaction Bundle of type 'transaction' containing the required MHD resources: a List resource representing the SubmissionSet, a DocumentReference resource for each document, optionally a List resource for a Folder, and a Binary or DocumentReference.content.attachment for the document content itself.
2. Populate the SubmissionSet List with required metadata: sourceId (the submitting organization OID), submissionTime, and references to the included DocumentReference entries.
3. Populate each DocumentReference with required MHD metadata: patient, date, type, category, content (attachment with contentType and either data or url), and context (encounter or period) as applicable — verify required elements against the current IHE MHD IG.
4. Set Bundle.entry.request.method to POST for new resources and include appropriate fullUrl values using temporary UUIDs for cross-resource references within the Bundle.
5. POST the transaction Bundle to the Document Recipient actor's FHIR endpoint (typically [base]/ for a transaction Bundle) and evaluate the returned transaction-response Bundle.
6. Check each entry in the response Bundle for status codes; a successful submission will show 201 Created for each entry; any 4xx or 5xx indicates a submission error requiring correction.