Support Client Headers passing conveniently

[lasteris]

For now, we have found the way below to pass headers:

        Map<String, List<String>> headers = Map.of("Authorization", List.of("Bearer ..."));
        requestContext.put(Message.PROTOCOL_HEADERS, headers);

But it would be cool, if we have method to pass headers as much convenient as we're doing in Quarkus Rest/Quarkus RestClient.
From application.properties, if it is fair for all requests.
From @Header/@ClientHeader or something annotation, if we need to do it per request.

Also, for Bearer Authorization, maybe worth to do as Quarkus CXF dealing with basic auth:

quarkus.cxf.client.basicAuth.username = bob
quarkus.cxf.client.basicAuth.password = bob234

[ppalaga]

Citing @maxandersen https://quarkusio.zulipchat.com/#narrow/channel/187030-users/topic/.E2.9C.94.20quarkus-cxf/near/482058993 :

for inspiration: rest client got a bunch of ways to enable custom headers - maybe similar can be applied to cxf clients? https://quarkus.io/guides/rest-client#custom-headers-support