Fix clientwide mypy errors

[tsmith023]

This PR implements a number of small fixes to ready the package for full mypy compliance

Once it's established, a pre-commit hook and a Github action will be added that run mypy sweeps of the codebase

In this initial PR, only /weaviate will be type checked but in future this should be extended to /test and /integration

[dirkkul]

very cool :)

[weaviate-git-bot]

Great to see you again! Thanks for the contribution.

beep boop - the Weaviate bot 👋🤖

PS:
Are you already a member of the Weaviate Slack channel?

[codecov-commenter]

Codecov Report

Patch coverage: 91.91% and project coverage change: -0.55% ⚠️

Comparison is base (eb3bf16) 95.43% compared to head (92332b8) 94.88%.
Report is 127 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #482      +/-   ##
==========================================
- Coverage   95.43%   94.88%   -0.55%     
==========================================
  Files          64       72       +8     
  Lines        8165     8658     +493     
==========================================
+ Hits         7792     8215     +423     
- Misses        373      443      +70     

Files Changed	Coverage Δ
weaviate/util.py	91.01% <72.91%> (-5.32%)	⬇️
weaviate/batch/crud_batch.py	78.11% <75.00%> (-17.21%)	⬇️
weaviate/schema/crud_schema.py	81.98% <80.55%> (+3.82%)	⬆️
weaviate/connect/connection.py	89.30% <83.87%> (+0.36%)	⬆️
weaviate/gql/aggregate.py	82.97% <85.45%> (+7.11%)	⬆️
mock_tests/test_exception.py	87.50% <87.50%> (ø)
weaviate/connect/authentication.py	96.15% <87.50%> (+8.15%)	⬆️
weaviate/exceptions.py	90.69% <87.50%> (-0.74%)	⬇️
weaviate/classification/config_builder.py	98.82% <88.88%> (-1.18%)	⬇️
weaviate/gql/filter.py	93.95% <93.69%> (-0.40%)	⬇️
... and 28 more

... and 6 files with indirect coverage changes

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