Sync current Python and Django versions

[amureki]

• Added support for Python 3.10 and 3.11
• Added support for Django 4.0 and 4.1
• Dropped support for Python 3.6
• Dropped support for Django 2.2 and 3.1
• Dropped custom app initializer for Django < 3.2

Check https://endoflife.date/python and https://endoflife.date/django for active versions information.

[amureki]

@Bogdanp that one is green and ready for a review. :)

[Bogdanp]

Thanks! I'll review the other PR this weekend.