title: Set different primary key in Active Admin (Rails)
body: <p>I'm using Active Admin as my interface for a rails project (client's request). The problem is... most of the tables in my client's database have primary key fields named 'something_id' instead of plain 'id'. This poses a big problem as Active Admin looks for an 'id' field and, since it doesn't find one, it basically crashes the page with an error:</p>
  
  <pre><code>Mysql2::Error: Unknown column 'buzz_articles.id' in 'order clause': SELECT  `buzz_articles`.* FROM `buzz_articles` ORDER BY buzz_articles.id desc LIMIT 30 OFFSET 0
  </code></pre>
  
  <p>I've tried running <code>set_primary_key :article_id</code> in the resource, but it's not recognized.</p>
  
  <p>Any help? Please??</p>