Generating or Retrieving Signed RDP Files

Hi,

I can see there's an option in the WVD HTML5 client to retrieve the RDP file required to launch an app. As an integrator, we're trying to do this programatically. Is there a way to retrieve the signed RDP file for an app via an API (I can't see anything in the latest REST API docs) or is there a supported way of us signing the files ourselves before handing them to the Virtual Desktop client?