[REQ] Improve python test coverage

Is your feature request related to a problem? Please describe.

The currently generated python code has a relatively low test coverage:

I think it would make sense to generate additional tests to improve the coverage especially for:

api_client.py ApiClient class
configuration.py Configuration class
exceptions.py all exception classes
rest.py RESTClientObject and RESTResponse class
default_api.py DefaultApi class

generated models: to_str, to_json, to_dict and from_dict methods

Describe the solution you'd like

Additional automatically generated tests that cover the files and classes mentioned above.

Additional context

This is the openapi.json file used for this code:
example_openapi.json

This is how the code was generated

docker run --rm -v "PATH_TO_REPO:/local" openapitools/openapi-generator-cli generate -i /local/omnitracker_service/example_openapi.json -g python -o /local/omnitracker_service/generated_code --additional-properties=packageName=omnitracker_openapi_client

Start with example_openapi.json and the Docker generation command, then inspect generated api_client.py, configuration.py, exceptions.py, rest.py and default_api.py. Review the generated model methods to identify the requested test coverage. Done means the generated Python client has tests covering these classes, exception types, REST behavior and model serialization methods.