title: Form_tag parameters in nested hash
body: <p>I have a form that doesn't have a model associated with it, so I'm using <code>form_tag</code> rather than <code>form_for</code>.  As expected, when the user submits the form each of the fields is included in the params hash. But the form will change a lot and I would prefer to have a hash within the params hash that will hold all of the form field values so that I don't have to change my controller every time I change my form.</p>
  
  <p>Is there a way to put the form field values into a nested hash like form_for does?  I'd like to be able to take all of the form fields and convert them to json by doing something like <code>params[:form_fields].to_json</code></p>