Add Python 3.12 support

[rtibbles]

Summary

Cleans up Django deprecation warnings
Adds Python 3.12 to the test matrix
Adds explicit support to setup.py
Updates testing dependencies so that pytest will run under Python 3.12
Removes coverage reporting, as it was breaking tests for Python 3.11 and 3.12, and we weren't uploading the coverage reports anywhere (running without coverage reporting also seems to shave off about 4-5 minutes from the overall test time).

TODO

• Have tests been written for the new code?
• Has documentation been written/updated?
• New dependencies (if any) added to requirements file

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Issues addressed

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Documentation

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