title: populating own error-messages to the grails domain errors
body: <p>I'd like to know, if (and how) I could append some own error-messages to the domain-object after (or before) a validation.</p>
  
  <p>My intention is, I have to check the uploaded file in a form for some attributes (image size etc.) and if something is wrong, I would like to add an error-message which is displayed in the usual grails ".hasErrors" loop.</p>
  
  <p>(And I think I need to have the possibility to express errors in some cross-domain check failure...)</p>
  
  <p>Thanks in advance,
  Susanne.</p>