title: Update nested attributes objects independently from parent model
body: <p>I have a parent model <code>'page'</code> and <strong>nested attributes</strong> model <code>'page_modules'</code> which at same time are modeled by <em>'Single Table Inheritance'</em> pattern.</p>
  <p>My problem is when I try to save different generated <code>'page_modules'</code>, if one of these is not validated, the whole model and nested attributes are not updated, even if some of these nested attributes pass the validation. ¿Is there a way to update all the validated <code>'page_modules'</code> and only refuse not validated <code>'page_modules'</code>?</p>