Feat: #21665 [dart][dart-dio] CopyWith for json_serializable

[LahaLuhem]

1. Add @CopyWith annotation to class template.
2. Add the required packages in the pubspec template

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[wing328]

https://github.com/OpenAPITools/openapi-generator/actions/runs/16630423609/job/47085879739?pr=21667

please follow step 3 to update the samples

[LahaLuhem]

@wing328 Regenerated them 👍🏽

[wing328]

Thanks for the PR but your commit (as shown in the Commits tab) is not linked to your Github account, which means this PR won't count as your contribution in https://github.com/OpenAPITools/openapi-generator/graphs/contributors.

Let me know if you need help fixing it.

Ref: https://github.com/OpenAPITools/openapi-generator/wiki/FAQ#how-can-i-update-commits-that-are-not-linked-to-my-github-account

[LahaLuhem]

@wing328 Nice catch, I forgot to do rituals after cloning the repo. My commit verfication is broken since forever, do you prefer that I fix it first?
Otherwise fixed it for now. Lmk if you want a specific style for the commit messages or so.

[LahaLuhem]

I think I forgot to add in the actual import for it. I'll add it now

[wing328]

since there's no further question/feedback, i've just merged it.

thanks for the contribution.