Public model_name_for_type method

[Exelord]

Hi,
I just think this method could be used in many cases associated with polymorphic relations like filtering by polymorphic model type. In that case having this public could make it easier to implement.

[lgebhardt]

@Exelord Looking at it a little closer the method should probably be a class method and moved down to the self section. I should have caught that in #882. How about renaming it to something closer to resource_type_for, which is it's reciprocal, such as model_name_for_type or just model_name_for.

  class << self
  #...
      def model_name_for_type(type)
        type_class_name = type.to_s.classify
        resource = resource_for(type_class_name)
        resource ? resource._model_name.to_s : type_class_name
      end
  end

[Exelord]

@lgebhardt You are right! I just forgot about moving it to self. I applied your feedback with method name and fixed tests :)

If u have more ideas or comment, go on!

Thanks :)

[lgebhardt]

@Exelord Thanks!

[toobulkeh]

How can this new feature be used?

Trying to see if it's something that can temporarily be used for #927