Reference scope by same name as serialization scope

By default, the serialization scope uses current_user, and you can
now reference the scope as "current_user" in the serializer. If you
override the scope using "serialization_scope" in your controller,
it will use that method name instead.

lib/active_model/serializer.rb

@@ -261,6 +261,13 @@ module ActiveModel
 
     def initialize(object, options={})
       @object, @options = object, options
+
+      scope_name = @options[:scope_name]
+      if scope_name && !respond_to?(scope_name)
+        self.class.class_eval do
+          define_method scope_name, lambda { scope }
+        end
+      end
     end
 
     def root_name