Add support for Rails 8.0

[phlipper]

Overview

This PR adds support for Rails 8.0 which has been officially released: https://rubyonrails.org/2024/11/7/rails-8-no-paas-required.

Notes

• Update Appraisals
• Update CI Workflow
• Add a new CHANGELOG entry

Thank you for all of your great work on this gem!

[djch]

Onya for the PR. As far as I can tell this gem is why I can't update my Spina projects to Rails 8 yet 😅

Could not find compatible versions

Because attr_json < 0.6.0 depends on activerecord >= 5.0.0, < 5.3
  and attr_json >= 0.6.0, < 1.3.0 depends on activerecord >= 5.0.0, < 6.1,
  attr_json < 1.3.0 requires activerecord >= 5.0.0, < 6.1.
And because attr_json >= 1.3.0, < 1.4.0 depends on activerecord >= 5.0.0, < 6.2
  and attr_json >= 1.4.0, < 2.0.0.rc1 depends on activerecord >= 5.0.0, < 7.1,
  attr_json < 2.0.0.rc1 requires activerecord >= 5.0.0, < 7.1.
And because attr_json >= 2.0.0.rc1, < 2.2.0 depends on activerecord >= 6.0.0, < 7.1
  and attr_json >= 2.2.0, < 2.4.0 depends on activerecord >= 6.0.0, < 7.2,
  attr_json < 2.4.0 requires activerecord >= 5.0.0, < 7.2.
Because every version of spina depends on attr_json >= 0
  and attr_json >= 2.4.0 depends on activerecord >= 6.0.0, < 7.3,
  every version of spina requires activerecord >= 6.0.0, < 7.3 or attr_json >= 0, < 2.4.0.
Thus, every version of spina requires activerecord >= 5.0.0, < 7.3.
And because rails >= 8.0.0 depends on activerecord = 8.0.0,
  every version of spina is incompatible with rails >= 8.0.0.
So, because Gemfile depends on rails ~> 8.0
  and Gemfile depends on spina >= 0,
  version solving has failed.

[jrochkind]

Perfect, thank you! You beat me to it.

[jrochkind]

2.5.0 released