title: how to permit one of the parameters to be arbitrary hash using strong_parameters?
body: <p>I have a model with one of the fields being <code>serialise :config, JSON</code>.</p>
  
  <p>it should permit any hash as a value. But I can't quite see a clean way to do it with <code>strong_parameters</code>.</p>
  
  <p>my current solution is:</p>
  
  <pre><code>def resource_params
    p = params.require(:model)
    config = dp.slice(:config).permit!
    p.delete(:config)
    [p.permit(:foo, :bar, ...).merge(config)]
  end
  </code></pre>