PTFE-693: unit test for settings class

[Abubakarr99]

No description provided.

[tcarmet]

Optionally add a testcase with errors expecting to be raised:

What happens when you do:

Settings(redis_om_url="toto")

Can be tested like:

with pytest.raises(<expected exception>):
    Settings(redis_om_url="toto")

[codecov-commenter]

Codecov Report

Merging #309 (f49805f) into main (5c1af0b) will increase coverage by 0.43%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #309      +/-   ##
==========================================
+ Coverage   90.04%   90.47%   +0.43%     
==========================================
  Files          13       13              
  Lines         231      231              
==========================================
+ Hits          208      209       +1     
+ Misses         23       22       -1     

Flag	Coverage Δ
api	19.91% <50.00%> (ø)
unit	81.81% <100.00%> (+0.43%)	⬆️

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Files Changed	Coverage Δ
runner_manager/models/settings.py	100.00% <100.00%> (+4.54%)	⬆️