Restore reverted lazy-loaded AR

This reverts commit c54cb7c.

Author: mpraglowski

ruby_event_store-active_record/lib/ruby_event_store/active_record.rb

@@ -15,6 +15,9 @@
 require_relative "active_record/index_violation_detector"
 require_relative "active_record/pg_linearized_event_repository"
 require_relative "active_record/version"
-require_relative "active_record/skip_json_serialization"
-require_relative "active_record/event"
-require_relative "active_record/railtie" if defined?(Rails::Engine)
+if defined?(Rails::Engine)
+  require_relative "active_record/railtie"
+else
+  require_relative "active_record/skip_json_serialization"
+  require_relative "active_record/event"
+end

ruby_event_store-active_record/lib/ruby_event_store/active_record/railtie.rb

@@ -3,6 +3,12 @@
 module RubyEventStore
   module ActiveRecord
     class Railtie < ::Rails::Railtie
+      initializer "ruby_event_store-active_record" do
+        ActiveSupport.on_load(:active_record) do
+          require_relative "../active_record/skip_json_serialization"
+          require_relative "../active_record/event"
+        end
+      end
     end
   end
 end