With the commit 3324e28804 ActiveRecord::SessionStore is extracted out of Rails into a gem ‘activerecord-session_store’. Setting config.session_store to :active_record_store will no longer work and will break if the activerecord-session_store gem isn’t available.
Earlier whenever we wanted to create a HABTM join table, we do this like: Now, in edge rails after this commit we can use a migration helper for the same: