Deleter must exist - AR-51 branch - With paranoia gem

[allhailskippy]

In the AR-51 branch, when Rails.application.config.active_record.belongs_to_required_by_default is set to true (which it is by default), and when using paranoia v2 for soft deletes, you cannot save the record because it is expecting deleter to be set (which it shouldn't be unless you are deleting it)

Could possibly be fixed by changing lib/active_record/userstamp/stampable.rb line 87 to include the optional: true as part of the merge.

belongs_to :deleter, relation_options.reverse_merge(foreign_key: config.deleter_attribute, optional: true) if associations.third