[DPE-8932] Strict mode configuration

[dragomirp]

Port of #1389

Issue

Solution

Checklist

• I have added or updated any relevant documentation.
• I have cleaned any remaining cloud resources from my accounts.

[codecov]

Codecov Report

❌ Patch coverage is 74.07407% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 75.87%. Comparing base (5b966b0) to head (5a258ce).

Files with missing lines	Patch %	Lines
src/charm.py	71.42%	1 Missing and 3 partials ⚠️
src/cluster.py	62.50%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1395      +/-   ##
==========================================
+ Coverage   75.79%   75.87%   +0.08%     
==========================================
  Files          17       17              
  Lines        4408     4415       +7     
  Branches      672      672              
==========================================
+ Hits         3341     3350       +9     
+ Misses        834      833       -1     
+ Partials      233      232       -1     

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