Provide a service attribute in page definition

The service can be any class that is callable and that is inheriting the service structure of Alchemy::BasePageService.

Author: kulturbande

app/models/alchemy/page_definition.rb

@@ -20,6 +20,7 @@ class PageDefinition
     attribute :hide, :boolean, default: false
     attribute :editable_by
     attribute :hint
+    attribute :service, Alchemy::PageServiceType.new
 
     # Needs to be down here in order to have the attribute reader
     # available after the attribute is defined.

spec/models/alchemy/page_definition_spec.rb

@@ -20,6 +20,7 @@ module Alchemy
       it { is_expected.to have_key(:hide) }
       it { is_expected.to have_key(:editable_by) }
       it { is_expected.to have_key(:hint) }
+      it { is_expected.to have_key(:service) }
     end
 
     describe "#blank?" do