can't modify frozen hash error from #serializable_attributes in Rails 8

[dbackeus]

When attempting to upgrade an app using active_model_otp to Rails 8 we started seeing error: can't modify frozen Hash errors when passing options into to_json on a model with has_one_time_password.

The error triggers at:
https://github.com/heapsource/active_model_otp/blob/main/lib/active_model/one_time_password.rb#L118

It seems that Rails 8 freezes incoming options for #serializable_attributes, making this mutation illegal.

[isaaclyman]

I'm seeing the same issue on a very simple Rails 8 app that doesn't use active_model_otp. It seems to be an issue with Rails, ActiveRecord, and Serializers, probably not caused by this library.

[tindron]

There may be more than one library that causes this issue, but this one should still be fixed.

In my case I started seeing it after updating to the oj 3.16.13. This change appears to be turning nil options into {} which activesupport then freezes: https://github.com/ohler55/oj/pull/984/changes

[dbackeus]

For the record there is a PR up with a fix: #135

We've been running a fork with the same fix applied for a long time without issues.