Fix some openapi warnings

[hmpf]

Test by visiting "/api/v1/schema/swagger-ui/" and "/api/v2/schema/swagger-ui/" without and with these commits, the list of warnings dumped to the terminal should be shorter.

Does not fix:

• ?: (urls.W005) URL namespace 'v2:auth' isn't unique. You may not be able to reverse all URLs in this namespace (Fix warning about namespaces when visting the autogenerated OpenAPI #901)
• Warning: encountered multiple names for the same choice set (EventTypesEnum). This may be unwanted even though the generated schema is technically correct. Add an entry to ENUM_NAME_OVERRIDES to fix the naming. (Fix warning about multiple enum names when visting the autogenerated OpenAPI #902)

I have no idea where to start on the first, as for the last, I cannot figure out where drf-spectacular finds something to interpret as EventTypesEnum. There is also TypeEnum with the same contents. Setting ENUM_NAME_OVERRIDES does nothing.

Also does not fix (#903):

• src/argus/filter/filters.py: Warning [IncidentViewSet > IncidentFilter]: Exception raised while trying resolve model field for django-filter field "tags". Defaulting to string (Exception: 'tags')
• src/argus/filter/filters.py: Warning [SourceLockedIncidentViewSet > SourceLockedIncidentFilter]: Exception raised while trying resolve model field for django-filter field "tags". Defaulting to string (Exception: 'tags')
• src/argus/filter/filters.py: Warning [IncidentViewSetV1 > IncidentFilter]: Exception raised while trying resolve model field for django-filter field "tags". Defaulting to string (Exception: 'tags')
• src/argus/filter/filters.py: Warning [SourceLockedIncidentViewSetV1 > SourceLockedIncidentFilter]: Exception raised while trying resolve model field for django-filter field "tags". Defaulting to string (Exception: 'tags')

I'm thinking fixing one of the above will yield the solution for all four.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 82.75862% with 5 lines in your changes missing coverage. Please review.

Project coverage is 84.18%. Comparing base (1849ec9) to head (988f957).
Report is 9 commits behind head on master.

Files with missing lines	Patch %	Lines
src/argus/site/serializers.py	64.28%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #897      +/-   ##
==========================================
- Coverage   84.20%   84.18%   -0.03%     
==========================================
  Files          89       90       +1     
  Lines        4040     4065      +25     
==========================================
+ Hits         3402     3422      +20     
- Misses        638      643       +5     

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[elfjes]

I'm not sure how to review this. I think it looks fine. Doensn't seem to impact us. Always good to fix warnings

[podliashanyk]

Tested it manually and it does what it promises.
This one probably needs a changelog fragment, and there is an unused import that can be removed

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud