title: Active Admin batch edit products with a preset collection
body: <p>Is there a way to add batch edit to Active Admin with a preset collection? My product model contains a <code>category</code> field.</p>
  
  <p>My ActiveAdmin's form looks like this :</p>
  
  <pre><code>f.input :category,as: :radio, collection:['cat1', 'cat2', 'cat3']
  </code></pre>
  
  <p>So I can choose a category within a collection. I would like to add batch edit so I could check many fields and then assign them a category from the previous collection.</p>
  
  <p>My first idea was to add many batch actions (one for cat1, one for cat2, one for cat3, etc. However, the batch actions menu would then contain more than 10 elements...</p>
  
  <p>There must be a better way to do this, is it?</p>