Add FHIR Terminology Service

[zgypa]

The Plan is to transform this into a light-weight terminology service. So possibly still have the static classes, which get imported, have the UI from medoco/tops-dicom, possibly separate the terminology part from the DICOM part, so that tops-dicom only has the DICOM and would look up the ConceptMaps here to find out what to use to encode the MWL.

The service should therefore have a way to also associate the DICOM object with each other, essentially replicating the existing logic that is in tops-dicom.

The end user would then have a single entry point, to configure all mappings for the entire network. For example, query this service with a procedure_id of system tops and ask the equivalent DICOM code, which should return a code that can be used for a Requested Procedure. Then query again to get procedure steps, which would return a ValueSet or procedure Steps, and so on.

I think we would use CodeSystems to list all codes per context, so there would be a DICOM Requested Procedure CodeSystem, with a list of all availble codes in there, then another for Scheduled Procedure Steps, and so on.

[zgypa]

I have created the branch and started importing stuff from tops-dicom. However nothing is tested and working yet. Consider using fastapi for fhir?

[zgypa]

Started creating unittest functions to test the most important and used /ValueSet/$expand endpoint. Other tests generated by chatgpt, but not useful, i commented them out. I had to create a property for the url of ValueSet becauese of pydantic.