This patch changes the base class of the Active Record model in app/models to ApplicationRecord.
This is in accordance with the change of model inheritance from ActiveRecord::Base to ApplicationRecord in Rails 5.
Reference link: https://www.bigbinary.com/blog/application-record-in-rails-5
However, the include destination of lib/plugins/acts_as_xxx will also change from ActiveRecord::Base to ApplicationRecord when this patch is applied,
This will affect the Active Record model of Redmine plugins that use the acts_as_xxx method, and the base class will need to be changed to ApplicationRecord.