Add support for CastsInboundAttributes

[sforward]

Summary

This PR adds support for custom cast classes that implement the CastsInboundAttributes interface ( https://laravel.com/docs/9.x/eloquent-mutators#inbound-casting). Currently the Cast class will incorrectly end up as return value of the attribute.

Type of change

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update
• [ ] Misc. change (internal, infrastructure, maintenance, etc.)

Checklist

• [x] Existing tests have been adapted and/or new tests have been added
• [x] Add a CHANGELOG.md entry
• [ ] Update the README.md
• [x] Code style has been fixed via composer fix-style

[mfn]

Pinging @barryvdh once more 🙏🏼 PR still LGTM; not sure how cleanly it applies currently though.

Maybe @sforward has the time to sync it with master and make sure it's good (changelog especially)

[sforward]

Sure, I have rebased the code again. I'm willing to help testing PR's if that's the current bottleneck of this repo.

[mfn]

I'm willing to help testing PR's if that's the current bottleneck of this repo.

I think this is always welcome, I'm definitely not vetting PRs enough whose features I don't know well / not use.

Ultimate it's up to @barryvdh for merging and I try to assist where time permits. Technically I've the ability to merge stuff, but we've a social agreement that he's the decision maker.

For this particular PR, I've no doubts about the technical part and my approval+merge still stands 😄