title: ActiveAdmin: Modifying Index Table Based on Active Scope
body: <p>Suppose I have an ActiveAdmin model with two scopes like so:</p>
  
  <pre><code>ActiveAdmin.register Book do
  
    scope :all, default: true
    scope :smith #all books by author 'smith'
  
    index do
      column :title
      column :published_year
      column :author
    end
  end
  </code></pre>
  
  <p>I don't want/need the 'author' column when the user has selected the 'smith' scope.</p>
  
  <p>So is there a way to get access to the current scope and only show the author column in one of the scopes?  I suppose for this example I could use a custom view and check the actual content of the data but I am hoping there is an easier and better way.</p>