fix: make airflow opa auth manager compatible with python 3.9

[razvan]

Description

Needed for: stackabletech/airflow-operator#573

Python 3.9:

❯ docker run --rm --entrypoint bash -ti -v $PWD:/app -w /app python:3.9
root@edd3f3d06c54:/app# pip install poetry \
&& poetry install \
&& poetry run pytest
...
Installing the current project: opa-auth-manager (0.1.0)
platform linux -- Python 3.9.21, pytest-8.3.4, pluggy-1.5.0
rootdir: /app
configfile: pyproject.toml
plugins: anyio-4.8.0
collected 19 items
                                                                                                                                                                                                                                                               
tests/test_opa_fab_auth_manager.py ...................[100%]

Python 3.12:

❯ docker run --rm --entrypoint bash -ti -v $PWD:/app -w /app python:3.12
root@a06b8984f214:/app# pip install poetry \
> && poetry install \
> && poetry run pytest
...
Installing the current project: opa-auth-manager (0.1.0)
platform linux -- Python 3.12.9, pytest-8.3.4, pluggy-1.5.0
rootdir: /app
configfile: pyproject.toml
plugins: anyio-4.8.0
collected 19 items
                                                                                                                                                                                                                                                               
tests/test_opa_fab_auth_manager.py ...................[100%]

[siegfriedweber]

Thanks!