title: How to pass form errors in session or flash? [Rails 2.3.5]
body: <p>I have a create action for a form that potentially generates errors (i.e. first name is missing) and then redirects.</p>
  
  <p>The problem is, that when the redirect happens those form errors get lost.
  How could I pass those form errors in a session to be displayed back in the original form (which should still be filled out with the previous details, as in the original error_messages behavior)?</p>
  
  <p>Thanks!</p>
  
  <hr>
  
  <p>The code:</p>
  
  <pre><code>def create
    @contact = Contact.new(params[:contact])
    if @contact.save
      flash[:notice] = "Sent."
    else
      flash[:notice] = "Error."
    end
  end
  </code></pre>