Improve Version Upgrade Mechanism for Internal FHIR Resources

[hhund]

Our mechanism for managing internal FHIR resources might need some improvements. We should discuss how different kinds of changes to internal FHIR resources should be handled. Examples could be:

1. Adding a new resource
   Add the new resource.
2. Removing a (not needed) resource
   Mark the old resource as retired? Delete the old resource, if it exists? Also delete all resources with reference/dependency to this resource?
3. Changing a resource (e.g. StructureDefinition) in a way not compatible with the previous version.
   Keep the old resource as retired and change all references to this resource to be version specific?
4. ...