dual api support for http client api in work item handler

Fair enough. Since this is an exception, maybe it would be worth documenting it in the code? I am just trying to look at this from the point of view of someone who does not understand all the details here. When I see upper case for field name I immediately look if its a `final`. If not I am just wondering why - should it be? Or should it not use upper case? Or maybe this is some kind of exception? The comment could make this a bit clearer. Just my $0.02.