tests: add unittests

[axodentally]

Add tests for the files in contact_player/*.

TODO:

• update sbom.json with new pytest dependency

commits:

• chore: add pytest dependency
• tests: add cases for ccp.py
• tests: add cases for contact_player.py
• tests: add cases for scenario.py

[axodentally]

This change is part of the following stack:

• tests: add unittests #24 ◀
  • Introduce pyproject.toml, restructure installation #25
    • ci: add job to run pytest tests #26

_{Change managed by git-spice.}