title: Changing the id parameter in Rails routing
body: <p>Using Ruby on Rails 3's new routing system, is it possible to change the default :id parameter </p>
  
  <pre><code>resources :users, :key =&gt; :username
  </code></pre>
  
  <p>come out with the following routes</p>
  
  <pre><code>/users/new
  /users/:username
  /users/:username/edit
  ...etc
  </code></pre>
  
  <p>I'm asking because although the above example is simple, it would be really helpful to do in a current project I'm working on.</p>
  
  <p>Is it possible to change this parameter, and if not, is there a particular reason as to why not?</p>