code: def call(env)
        handle_queue(env["HTTP_X_REQUEST_START"])
  
        if test_path?(env["PATH_INFO"])
          build_test_response
        elsif info_path?(env["PATH_INFO"])
          build_info_response
        else
          @app.call(env)
        end
      end
docs: Initializes HireFire::Middleware.
  
   @param [Proc] app call with `env` to continue down the middleware stack.
  
   Intercepts and handles the /hirefire/test, /hirefire/development/info,
   and /hirefire/HIREFIRE_TOKEN/info paths. If none of these paths match,
   then then request will continue down the middleware stack.
  
   When HireFire::Resource.log_queue_metrics is enabled, and the HTTP_X_REQUEST_START
   header has been injected at the Heroku Router layer, queue time information will be
   logged to STDOUT. This data can be used by the HireFire Logdrain with the
   Web.Logplex.QueueTime autoscaling strategy.
  
   Important: Don't set/update instance variables within this- or any underlying methods.
   Doing so may result in race conditions when using threaded application servers.
  
   @param [Hash] env containing request information.