Django-admin-extra-buttons

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* moves to pyproject.toml (removes `setup.py`)
* starts using `uv`
* removes constraint to use `button` as link() argument
* drop official support for Django < 3.x

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* add common css class
* fixes permissions check

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* BUG FIX: fixes check() implementation
* Allow any HttpResponse as return value

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* pass request when basic_auth authenticate

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* minor refactoring of get_urls()

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* allow overwrite visible inside handler