Add optional description id extension

[danka74]

I had the need for adding description ids to ValueSet $expand result. The use case was to use FHIR $expand output as a basis for making batch description change requests to the SNOMED authoring platform. Also, there is a standard extension for description ids: https://build.fhir.org/ig/HL7/fhir-extensions//StructureDefinition-coding-sctdescid.html

There is a working branch in my fork: https://github.com/danka74/snowstorm/tree/description-ids
but would require unit tests and documentation.

The implementation adds a new parameter to the $expand operation definition "includeDescriptionId" which if it's =true adds the extension above to the FHIR expansion results.

Cheers,
Daniel

[kaicode]

Thanks Daniel, this looks good.
We will take this when we can.

[kaicode]

Is there a standard for the request parameter name? The fork uses includeDescriptionId.

[kaicode]

(Internal ticket ISTO-124 )

[danka74]

I don't think there is a standard parameter name, and something like x-include-description-id could be an option which more clearly states it's a non-standard parameter.

Further, I can go ahead and create unit tests and documentation.

[kaicode]

That new suggested parameter name looks good to me.
Please do add tests and documentation if possible.