refactor the method cache objects to have a superclass
remove deprecated `PostgreSQLAdapter#outside_transaction?` method.
cleanup, remove trailing whitespace from guides/CHANGELOG
Removed deprecated threadsafe!
Merge pull request #11279 from jetthoughts/removed_threadsafe_deprectaed_option

Removed deprecated threadsafe! from Rails Config
Correctly handle relations as values in where() for polymorphic associations.