Allow admins to view and edit users

[lkeegan]

• backend
  • add /admin/users/ endpoint to get a list of users
  • refactor admin endpoints into separate files for languages, milestones, users, questions
  • refactor tests to also create a temporary in-memory users database for each test
    • add pytest-asyncio to allow use of async fixtures
  • refactor tests to be fully independent of each other
    • new app & new temp dirs for each test
    • makes test suite slower to run but easier to maintain
  • remove DATA_FILES_PATH as we already have STATIC_FILES_PATH and PRIVATE_FILES_PATH
• admin-frontend
  • add users tab with table of users whose permissions can be edited
• resolves Add Users tab to admin interface #164

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 87.97251% with 35 lines in your changes missing coverage. Please review.

Project coverage is 31.01%. Comparing base (d71691a) to head (d79fe2d).

Files with missing lines	Patch %	Lines
frontend/src/lib/components/Admin/Users.svelte	0.00%	32 Missing and 1 partial ⚠️
frontend/src/lib/components/AdminPage.svelte	0.00%	1 Missing ⚠️
.../src/mondey_backend/routers/admin_routers/users.py	92.30%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #168      +/-   ##
==========================================
+ Coverage   30.39%   31.01%   +0.61%     
==========================================
  Files          95      100       +5     
  Lines        3287     3373      +86     
  Branches       92       93       +1     
==========================================
+ Hits          999     1046      +47     
- Misses       2218     2256      +38     
- Partials       70       71       +1     

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[sonarcloud]

Quality Gate passed

Issues
3 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[MaHaWo]

maybe it would be better to remove the default image entirely here.

[lkeegan]

maybe it would be better to remove the default image entirely here.

true, but I'll do it in a separate PR, with all the unrelated refactoring this PR has already diverged enough from what its title claims it is about!