build: upgrade base image & MongoDB; drop py3.8

[uniqueg]

Description

• Drop support for Python 3.8
• Upgrade Docker base image from Debian 11 "Bullseye" to Debian 12 "Bookworm"
• Add support for MongoDB versions "6.0" and "7.0" in CI
• Drop support for MongoDB version "4.2" from CI

Fixes #224
Fixes #226
Fixes #227

Type of change

Please delete options that are not relevant.

• Build update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have updated the documentation (or documentation does not need to be updated)
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have not reduced the existing code coverage

[sourcery-ai]

Hey @uniqueg - I've reviewed your changes and they look great!

Here's what I looked at during the review

• 🟡 General issues: 2 issues found
• 🟢 Security: all looks good
• 🟢 Testing: all looks good
• 🟢 Complexity: all looks good

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (f6526be) to head (a655e92).
Report is 7 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff            @@
##               dev      #223   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           20        20           
  Lines          975       975           
=========================================
  Hits           975       975           

Flag	Coverage Δ
test_unit	100.00% <ø> (ø)

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[uniqueg]

closed in favor of #229