Add custom fields to invoice, odergroup, supplier and user

app/models/concerns/custom_fields.rb

@@ -0,0 +1,16 @@
+module CustomFields
+  extend ActiveSupport::Concern
+  include RailsSettings::Extend
+
+  attr_accessor :custom_fields
+
+  included do
+    after_initialize do
+      settings.defaults['custom_fields'] = { } unless settings.custom_fields
+    end
+
+    after_save do
+      self.settings.custom_fields = custom_fields if custom_fields
+    end
+  end
+end