FHIR consumer: support outgoing HTTP headers

[qligier]

I would like to set HTTP headers in a FHIR response when using a FHIR consumer, e.g. for Trace Context support, by using Constants.HTTP_OUTGOING_HEADERS.

I tried to check the code but could not find a place where Camel's exchange would exist alongside Hapi's HttpServletResponse, to map the headers from one to the other.
Is there any way to do it?