The case is I want my `{{render}}` to infer a controller name from supplied ember-data model's name automatically.

e.g. in `{{render 'animal' animal}}`, if `animal` is a `Cat`, I hope the template is rendered with a `CatController`

It seems that the render helper accepts a `controller=` parameter now, but then regards the parameter as a literal instead of a variable.

<https://github.com/emberjs/ember.js/blob/master/packages/ember-routing-handlebars/lib/helpers/render.js#L115>

For now, I just put the representation codes (needed by template) in target models, which I believe is bad.

What is the right way to implement this polymorphic-alike rendering?