rails/rails — pull request #8580 by balexand (2012-12-21 19:46:30+00:00)
Title: Include ActiveModel::Validations::Callbacks in ActiveModel::Model

`ActiveModel::Model` already includes `ActiveModel::Validations` and `ActiveModel::Callbacks`, but not `ActiveModel::Validations::Callbacks`. I think it would be handy to also include this module so methods like `before_validation` can be used. Thanks!