title: Symfony2 - Set minimum number of embedded forms
body: <p>Using the scenario in <a href="http://symfony.com/doc/current/cookbook/form/form_collections.html" rel="nofollow" title="How to Embed a Collection of Forms">How to Embed a Collection of Forms</a>, I would like to ensure that a <code>Task</code> always have at least 1 <code>Tag</code>. For my case however, the relationship of <code>Task</code> and <code>Tag</code> is <code>1:n</code> rather than <code>n:m</code>.</p>
  
  <p>I am particularly concerned on the scenario where all <code>Tags</code> are removed (I'd like to prevent this). How can I ensure that a <code>Task</code> form always have at least 1 <code>Tag</code>?</p>