title: How to use ActiveAdmin on models using has_many through association?
body: <p>I am using <a href="https://activeadmin.info/" rel="noreferrer">ActiveAdmin</a> gem in my project.</p>
  
  <p>I have 2 models using has_many through association. The database schema looks exactly the same as the example in RailsGuide. <a href="https://guides.rubyonrails.org/association_basics.html#the-has_many-through-association" rel="noreferrer">http://guides.rubyonrails.org/association_basics.html#the-has_many-through-association</a>
  <a href="https://i.stack.imgur.com/qaWFh.png" rel="noreferrer"><img src="https://i.stack.imgur.com/qaWFh.png" alt="has_many through association"></a><br>
  <sub>(source: <a href="http://guides.rubyonrails.org/images/has_many_through.png" rel="noreferrer">rubyonrails.org</a>)</sub>  </p>
  
  <p>How can I use ActiveAdmin to ...</p>
  
  <ol>
  <li>show appointment date of each patient in physicians page?</li>
  <li>edit appointment date of each patient in physicians page?</li>
  </ol>
  
  <p>Thanks all. :)</p>