AQI unit testing

[smannist]

Adds a few tests for functions related to aqi

[codecov]

Codecov Report

Merging #298 (51809d2) into main (eb95e2e) will increase coverage by 2.98%.
The diff coverage is 100.00%.

❗ Current head 51809d2 differs from pull request most recent head f724f03. Consider uploading reports for the commit f724f03 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #298      +/-   ##
==========================================
+ Coverage   80.55%   83.53%   +2.98%     
==========================================
  Files          55       56       +1     
  Lines        1445     1488      +43     
  Branches      169      170       +1     
==========================================
+ Hits         1164     1243      +79     
+ Misses        257      219      -38     
- Partials       24       26       +2     

Files Changed	Coverage Δ
recommender-back/src/tests/apis/aqi_test.py	100.00% <100.00%> (ø)
recommender-back/src/tests/apis/manager_test.py	95.45% <100.00%> (+1.01%)	⬆️

... and 2 files with indirect coverage changes

[Sidorow]

Looks good and tests pass locally.