Thanks @Muhammad Waseem !

I know about FHIR schema json opportunity and use it too.

But what I'm talking about here in this question is revealed in this video. 

Besides Patient resource we can submit "StructureDefinition" resource (listed above in a spoiler), which introduces constraints in the FHIR standard in this particular FHIR server I'm working with.

And the second example above is the Patient resource with this profile in meta section which FHIR server should use to "fire" constraints. But it doesn't.

@Patrick Jamieson , could you please help here?
 

Hi @Lorenzo Scalese ! Yes! It is in Location header, as @Tani Frankel mentioned. 

This is what I received in headers:

http://localhost:52773/fhir/r4/Patient//1983/_history/1
So, the id is 1983.

It is a bit different from what the public FHIR server on hl7.org/fhir returns - it returns the id also in a response.

Not sure though what is the "standard" behavior but if find it convenient enough to have the id in the response.