feat: add python 3.12 support

[BryanttV]

Description

This PR adds support to Python 3.12.

• The assertDictContainsSubset method was removed in Python 3.12. It was replaced with assertLessEqual(itemsA, itemsB)

Supporting information

• Drop Python 3.8 & Add Support for Python 3.12 #212
• Drop Python 3.8 & add support for Python 3.12 public-engineering#274

Checklists

Check off if complete or not applicable:

Merge Checklist:

• All reviewers approved
• Reviewer tested the code following the testing instructions
• CI build is green
• Version bumped
• Changelog record added with short description of the change and current date
• Documentation updated (not only docstrings)
• Code dependencies reviewed
• Fixup commits are squashed away
• Unit tests added/updated
• Noted any: Concerns, dependencies, migration issues, deadlines, tickets

Post Merge:

• Create a tag
• Create a release on GitHub
• Check new version is pushed to PyPI after tag-triggered build is
  finished.
• Delete working branch (if not needed anymore)
• Upgrade the package in the Open edX platform requirements (if applicable)

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[mariajgrimaldi]

Shouldn't we use the Python version used by the current release of the Open edX ecosystem, python 3.11 or are the services already using python 3.12? This question also applies to the other default changes.

[BryanttV]

Yeah, You're right. Done: fd79a6b

[mariajgrimaldi]

More context on this change: openedx/edx-cookiecutters@293ae2f