add support for Django 4.0, Python 3.10, drop support of Django 1.11

[PetrDlouhy]

Also #158 would be needed for compatibility with Django 3.x

[PetrDlouhy]

Seem like the tests doesn't have enough permissions to run in MRs.

[coordt]

@PetrDlouhy I have a branch that should fix these issues.

Can you review it and see if you think it is ready for merging, and I can merge it in. Then merging this branch might work better.

[codecov[bot]]

Codecov Report

Merging #167 (d24aab4) into master (0f09d7d) will increase coverage by 0.56%. The diff coverage is 77.50%.

@@            Coverage Diff             @@
##           master     #167      +/-   ##
==========================================
+ Coverage   64.97%   65.54%   +0.56%     
==========================================
  Files          24       24              
  Lines        1122     1126       +4     
  Branches      248      252       +4     
==========================================
+ Hits          729      738       +9     
+ Misses        299      294       -5     
  Partials       94       94              

Impacted Files	Coverage Δ
...gories/editor/templatetags/admin_tree_list_tags.py	45.37% <42.85%> (ø)
categories/editor/tree_editor.py	47.48% <55.55%> (+0.76%)	:arrow_up:
categories/registration.py	72.27% <75.00%> (+1.68%)	:arrow_up:
categories/admin.py	60.86% <100.00%> (ø)
categories/base.py	67.39% <100.00%> (ø)
...egories/management/commands/add_category_fields.py	87.50% <100.00%> (ø)
...egories/management/commands/drop_category_field.py	86.66% <100.00%> (ø)
categories/migration.py	83.67% <100.00%> (+7.58%)	:arrow_up:
categories/models.py	77.02% <100.00%> (ø)
categories/settings.py	52.38% <100.00%> (ø)
... and 4 more

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[PetrDlouhy]

@coordt I have rebased this to current master, fixed all remaining issues and make all tests work. I did drop support for out of date Django 1.11, because it doesn't support path/re_path in urls, that would be too difficult to support both formats.

[PetrDlouhy]

I have updated this and included also Django 4.1 with tests.

I had to also update black (already included in #169).

@coordt Could you please review this and make a new release of django-categories? It will be year soon from Django 4.0 release and there is still no released updated version.

[PetrDlouhy]

@coordt Thank you for your very quick reaction.