passing a nil in the polymorphic array is not supported. remove nils before you call the method
Move dup destroyed test to specific file that tests dup logic

Also change other related test to use existing record rather than
creating new one.
Add branch to arel on Gemfile to allow local bundle config [ci skip]
Add missing require to fix test :bomb:
Add support for module-level table_suffix in models

This makes table_name_suffix work the same as table_name_prefix when
using namespaced models. Pretty much the same as 67d1cec.