title: Use active_model_serializer with a non-ActiveRecord object
body: <p>I have a model object that is not descended from ActiveRecord::Base and is not stored in the database. I created a serializer for it (with the same name + "Serializer"), and in my controller I'm calling <code>render json: object_instance</code>.</p>
  
  <p>The result is an exception from deep inside of <code>render</code>.</p>
  
  <p>I implemented an <code>as_json</code> method that instantiates the serializer and calls it, but the result is then a missing method in the object, <code>read_attribute_for_serialization</code>.</p>
  
  <p>I want my object to act like an ActiveModel-compatible object at least as far as Active Model Serializer goes, but I don't see any reference to this in their documentation.</p>