Passing API Header in HTTP Target

My objective is to simply pass ticket information when a ticket is created to an external application using an HTTP API target. I am able to pass an API Key in the URL such as https://www.somewebsite.com/index.php/api/get_projects_and_boards/apikey/<key value> but that is an unsecure method and exposes my API key.

Similar to the "Form Encoded" method you can select when creating your HTTP target that gives you an option for a "key" and "Value," it would be extremely helpful if you were able to specify custom header keys to be passed in the api call.