mongoid/mongoid — pull request #3882 by Shwetakale (2014-12-11 07:11:46+00:00)
Title: checks added for :update_attribute for dynamic attributes refs #3875

When we call process_attribute, it does all the checks for ensuring that
dynamic attributes are allowed.

**Note** This impacts the `:counter_cache` option as it requires dynamic fields.
When using the counter_cache, the model must include
`Mongoid::Attributes::Dynamic`

refs #3875