Defer loading SettingObject until ActiveRecord is loaded (#119)

The gem was requiring `rails-settings/setting_object` at the top level,
which defines an ActiveRecord::Base subclass and causes ActiveRecord
to load too early. This interferes with Rails’ lazy-loading behavior (eg.
preventing new framework defaults from being applied correctly).

Moving the require statement into the `ActiveSupport.on_load(:active_record)`
block ensures it loads only when ActiveRecord is ready.

Author: ruimiguelsantos

lib/rails-settings.rb

@@ -1,9 +1,10 @@
-require 'rails-settings/setting_object'
 require 'rails-settings/configuration'
 require 'rails-settings/base'
 require 'rails-settings/scopes'
 
 ActiveSupport.on_load(:active_record) do
+  require 'rails-settings/setting_object'
+
   ActiveRecord::Base.class_eval do
     def self.has_settings(*args, &block)
       RailsSettings::Configuration.new(*args.unshift(self), &block)
@@ -12,4 +13,4 @@ def self.has_settings(*args, &block)
       extend RailsSettings::Scopes
     end
   end
-end
+end