You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: rack_session.rb
    path of file: ./repos/clearance/lib/clearance
    
    the code of the file until where you have to start completion: module Clearance
  # Rack middleware that manages the Clearanc
    
    def call(env)
      session = Clearance::Session.new(env)
      env[:clearance] = session
      response = @app.call(env)

      if session.authentication_successful?
        session.add_cookie_to_headers
      end