Allow providing map and models in the $transform operation

[qligier]

Fixes #305

We are not compatible with the official $transform operation because Brian's FHIRPath Lab uses resource instead of content, and we have not implemented all R5 parameters.

But this PR allows connecting Brian's FHIRPath Lab to Matchbox.

[oliveregger]

Thanks!

Could we add in addition test cases for the transform operation:

• one with the "traditional" matchbox call where we have the source paramater
• one which mimics the behaviour of brian fhir mapper?

added to the different API tests?

https://github.com/ahdis/matchbox/blob/main/matchbox-server/src/test/java/ch/ahdis/matchbox/test/MatchboxApiR4Test.java

there is a test ig where the we can put the example map inside:

https://github.com/ahdis/matchbox/blob/main/matchbox-server/src/test/resources/matchbox.health.test.ig.r4-0.1.0.tgz

source is in https://github.com/ahdis/matchbox-test-ig/tree/master

[qligier]

Sure!

Do we need to also split the provider between R4, R4B and R5 versions?
Currently, we parse everything as R5, although the engine supports having different contexts for the source and target. I don't see how you could provide an R5 StructureMap, and R4 models in the same Parameter resource.

[oliveregger]

I think all R5 should be fine (SD are normative), and we return the output of the mapping in the required version.