routes.rb

require "our_app"
require "we_can_use_our_middleware"

Rails.application.routes.draw do
  # we can mount directly
  mount OurNewApp => "/posts"
  
  # using Rack::Builder to add middleware
  
  mount Rack::Builder.new {
    use ApiKeyValidationMiddleware
    
    run OurNewApp
  }, to: "/secure_posts"
end