title: Grocery crud set_relation
body: <pre><code>$crud-&gt;set_relation('seo_url', 'db_projects','seo');
  </code></pre>
  
  <p>On <strong>insert/update</strong> crud add <strong>id</strong> (primary key ) from db_projects to <strong>seo_url</strong> field. How can I add <strong>seo</strong> from db_projects not <strong>id</strong> (primary key) to seo_url field?</p>