As part of the fix for CVE-2022-32224 Rails intruduced safe YAML loading
and the `ActiveRecord.yaml_column_permitted_classes` config.
PaperTrail added support for respecting the new configuration here
https://github.com/paper-trail-gem/paper_trail/pull/1397
The CVE-2022-32224 fix was also backported to Rails versions 5.2.8.1,
6.0.5.1, and, 6.1.6.1, however the name of the confiuration is slightly
different from that in Rails 7.x.
7.0.3.1 ActiveRecord.yaml_column_permitted_classes
6.1.6.1 ActiveRecord::Base.yaml_column_permitted_classes
6.0.5.1 ActiveRecord::Base.yaml_column_permitted_classes
5.2.8.1 ActiveRecord::Base.yaml_column_permitted_classes
PaperTrail currently doesn't support this alternative configuration
naming, which means it will silent fall back to unsafe YAML loading.
This commit updates `PaperTrail::Serializers::YAML` to be compatible
with safe YAML loading for the Rails 5.2 / 6.0 / 6.1 branches.
172ac1d747