Triggered when a user tries to delete an email template in the Administration Area.
The handler can throw an exception to cancel the template deletion. Example:
public function subscribeEvents()
{
Backend::$events->addEvent('onDeleteEmailTemplate', $this, 'process_template_deletion');
}
public function process_template_deletion($template)
{
if ($template->code == 'payment_notificaiton')
throw new Phpr_ApplicationException('You cannot delete this email template.');
}