title: How to make a concern route DRYer
body: <p>sometimes I need a concern route as a collection and sometimes as a member (sometimes I <code>have_many</code> galleries, and sometimes just <code>has_one</code>)</p>
  
  <pre><code>concern :single_galleriable do
    resource :gallery, concerns: :photoable do
      member do
        post :make_feature
      end
    end
  end
  
  concern :galleriable do
    resources :gallery, concerns: :photoable do
      member do
        post :make_feature
      end
    end
  end
  </code></pre>
  
  <p>and then I would do</p>
  
  <pre><code>resources :somemodel, concerns: :single_galleriable
  </code></pre>
  
  <p>obviously, too wet..</p>
  
  <p>can I use the concern as resource or resources according to my needs while the concern's content stay the same?</p>