title: Kohana auth login
body: <p>I'm trying to user kohana auth module, but i get the error:
  ' Call to undefined method Model_User::unique_key()'</p>
  
  <p>i user the code:</p>
  
  <pre><code>$auth = Auth::instance();
      if ($auth-&gt;login($_POST['email'], $_POST['password']))
      {
          echo 'hello, '.$auth-&gt;$_POST['username'];
      }
      else
      {
          echo 'login failed!';
      }
  </code></pre>
  
  <p>This happends when the email and password are ok.
  Do you know what is wrong?</p>