medication_request_references table contains normalized references from the medication request to other entities. It supports the following reference properties:
- medication_reference (required): links to the medication that was requested
- subject (required): links to the patient for whom the medication was requested
- encounter: links to the encounter where the request was made
- requester: links to the practitioner who made the request
- reason_reference: links to conditions or other reasons for the medication request
- medication_request_id
- patient_id
- medication_id

