[#1647] Add configurable warning banner

[pi-sigma]

Taiga: #1647

[codecov-commenter]

Codecov Report

Merging #728 (9712097) into develop (4e2861a) will increase coverage by 0.00%.
Report is 10 commits behind head on develop.
The diff coverage is 100.00%.

@@           Coverage Diff            @@
##           develop     #728   +/-   ##
========================================
  Coverage    96.24%   96.25%           
========================================
  Files          668      670    +2     
  Lines        23855    23867   +12     
========================================
+ Hits         22960    22972   +12     
  Misses         895      895           

Files Changed	Coverage Δ
src/open_inwoner/utils/context_processors.py	90.90% <ø> (ø)
src/open_inwoner/configurations/admin.py	100.00% <100.00%> (ø)
...nfigurations/migrations/0047_auto_20230809_0833.py	100.00% <100.00%> (ø)
src/open_inwoner/configurations/models.py	97.79% <100.00%> (+0.06%)	⬆️
src/open_inwoner/utils/templatetags/utils.py	91.11% <100.00%> (+0.20%)	⬆️

... and 7 files with indirect coverage changes

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[alextreme]

Looks fine to me, @jiromaykin can give this a double-check just in case

[jiromaykin]

I have added front-end feedback and requested changes that will be quite informative about how we use icons etc. in this project 🙂

[jiromaykin]

Some minor issues and it will be good to go.

[alextreme]

Creating test database for alias 'default'...
CommandError: Conflicting migrations detected; multiple leaf nodes in the migration graph: (0047_auto_20230809_0833, 0048_auto_20230816_1255 in configurations).
To fix them run 'python manage.py makemigrations --merge'

[jiromaykin]

If you finally remove the unused "static/img/exclamation-encircled.svg" file then I will approve it! 😄

[alextreme]

django.db.migrations.exceptions.NodeNotFoundError: Migration configurations.0049_siteconfiguration_extra_css dependencies reference nonexistent parent node ('configurations', '0048_auto_20230816_1255')