Drop Python 3.8 & Add Support for Python 3.12

[irtazaakram]

Description:

Follow and complete all of the following steps for the issue to be marked as done.

• [ ] Update the tox.ini, setup.py, setup.cfg, or pyproject.toml to remove Python 3.8 and add support for Python 3.12.
• [ ] Ensure GitHub Actions workflows, including the CI matrix, are updated to reflect the supported Python versions (3.11, and 3.12).
• [ ] Adjust any testing or build configurations to ensure compatibility with Python 3.12.
• [ ] Remove references to Python versions earlier than 3.11 from all relevant configuration files.
• [ ] Run all tests and verify they pass in the CI with the updated versions.
• [ ] Add a CHANGELOG entry: “Dropped support for Python 3.8 and added support for Python 3.12.”
• [ ] Bump the package version and release a new version on GitHub & PyPI (where applicable).

[mariajgrimaldi]

Python 3.8 version dropped from CI: https://github.com/openedx/openedx-events/pull/392. I'll be working on the Python 3.12 support.