Currently, you can only specify the method of an HTTP request for a Harbormaster Build Step, however some external build systems (such as TeamCity, which I'm targeting), require a post body that specifies build specifics instead of URL params. It would be nice to have a text box in an HTTP build step that a user could provide text of type application/xml or application/json and when the build is triggered by Phabricator, this body is sent with the HTTP POST.
I would also like to include the already provided injectable build variables into this POST body if the user deems it necessary.