code: def mount(mounted_app, path, options = {})
        mounted_app = MountedApplication.new(mounted_app, path, options)
        self.class.mounted_applications << mounted_app
        mounted_app
      end
docs: Mounts an application in the router as a sub application in the
   url space.  This will route directly to the sub application and
   skip any middlewares etc defined on a stack