WIP #1105 fix bug with inclusion and linkage of has_one polymorphic

Author: senid231

Diff for: lib/jsonapi/relationship.rb

@@ -41,6 +41,9 @@ def self.polymorphic_types(name)
             klass.reflect_on_all_associations(:has_many).select{|r| r.options[:as] }.each do |reflection|
               (hash[reflection.options[:as]] ||= []) << klass.name.downcase
             end
+            klass.reflect_on_all_associations(:has_one).select{|r| r.options[:as] }.each do |reflection|
+              (hash[reflection.options[:as]] ||= []) << klass.name.downcase
+            end
           end
         end
       end

Diff for: lib/jsonapi/resource.rb

@@ -1012,8 +1012,10 @@ def define_relationship_methods(relationship_name, relationship_klass, options)
       def define_foreign_key_setter(relationship)
         if relationship.polymorphic?
           define_on_resource "#{relationship.foreign_key}=" do |v|
-            _model.method("#{relationship.foreign_key}=").call(v[:id])
-            _model.public_send("#{relationship.polymorphic_type}=", v[:type])
+            model_id = v.nil? ? nil : v[:id]
+            model_type = v.nil? ? nil : self.class.resource_klass_for(v[:type].to_s)._model_class.to_s
+            _model.method("#{relationship.foreign_key}=").call(model_id)
+            _model.public_send("#{relationship.polymorphic_type}=", model_type)
           end
         else
           define_on_resource "#{relationship.foreign_key}=" do |value|