ToDo's: update tests and Github Actions

[A-Buch]

ToDo's:

• update dependabot with automerge
• merge/solve dependabot pull requests from February
• automatically correct files with Ruff pre-commit hook used with CI https://thomasthornton.cloud/2022/08/04/running-pre-commit-hooks-as-github-actions/, https://interrupt.memfault.com/blog/pre-commit#continuous-integration-ci
• fixture test_data
• update README: poetry env, automatic testing (fixtures and mocking, pre-commit hooks, CI, pytest and unitest)

maybe:

• test example with monkeypatching
• example with pytest-datadir

[A-Buch]

Black and Ruff autofix line-length
Wait until Black (or Ruff formatter) can handle various types of too long lines [E501].
black --preview (version 24.4.2) currently fixes a few versions of too long lines and fails for others.

• update pre-commit as soon as stable version for autofix of line-length is available