title: How to force custom Rails route to use :id instead of :<model>_id
body: <p>I defined the following custom Rails route in routes.rb: </p>
  
  <pre><code>resources :projects do
      get 'members' 
  end
  </code></pre>
  
  <p>This results in the following route (output from rake routes): </p>
  
  <pre><code>project_members GET        /projects/:project_id/members(.:format)
  </code></pre>
  
  <p>What I would like, though, is for the route to map to this instead (change :project_id to :id)</p>
  
  <pre><code>project_members GET        /projects/:id/members(.:format)
  </code></pre>
  
  <p>How can I make that happen?</p>