Setup testing for Python 3.10

[krzys-h]

Closes #614

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This change is 

[codecov[bot]]

Codecov Report

Merging #617 (72b0243) into master (8451a92) will increase coverage by 0.05%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #617      +/-   ##
==========================================
+ Coverage   84.33%   84.39%   +0.05%     
==========================================
  Files          15       15              
  Lines        2432     2441       +9     
==========================================
+ Hits         2051     2060       +9     
  Misses        381      381              

Impacted Files	Coverage Δ
...app/management/commands/populate_with_test_data.py	97.08% <0.00%> (+0.20%)	:arrow_up:

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[krzys-h]

@cytadela8 I broke the workflow syntax when switching the codecov version from 3.9 to 3.10 earlier, please reapprove