Comment:

While medicationCodeableConcept and medicationReference have overlap, there is a good reason to support BOTH in the resource at the same time. Many clients will need to have code to process the response, but little else from the Medication resource when the server makes use of the medication resource. It would be helpful to have a structure that requires at least one of medicationReference and medicationCodeableConcept without rejecting the fact that both MAY be present.

Summary:

Allow both medicationCodeableConcept and medicationReference