title: Yii custom model errors
body: <p>I am saving a model instance performing some actions in "beforeSave" model function.<br>
  I want to add some errors/messages to the model and then to get them in the controller and show to the user.<br>
  As far I have two ideas of how to implement this:  </p>
  
  <ul>
  <li>Use a dummy attribute with ActiveRecord function <code>"addError": $this-&gt;addError("dummy"=&gt;"my message");</code>    It is not the best way to do it as I'll have to invent new dummy attributes.  </li>
  <li>Add a new property "custom_errors" to the model and function "addCustomErrors"  </li>
  </ul>
  
  <p>Maybe there is a built-in way to do it or an extension?<br>
  Anyway how can I do it?</p>