[ci skip] - error_messages_for has been deprecated since 2.3.8 - lets reduce any confusion for users
Merge pull request #13657 from leriksen/master

[ci skip] - error_messages_for has been deprecated since 2.3.8 - lets re...
doc, API example on how to use `Model#exists?` with multiple IDs. [ci skip]

Refs #13658
Merge https://github.com/rails/rails