Fix sub_configs=True not working for callable types that return a class

[mauvilsa]

What does this PR do?

Fixes #419

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• Did you read the contributing guideline?
• [n/a] Did you update the documentation? (readme and public docstrings)
• Did you write unit tests such that there is 100% coverage on related code? (required for bug fixes and new features)
• Did you verify that new and existing tests pass locally?
• Did you make sure that all changes preserve backward compatibility?
• Did you update the CHANGELOG? (not for typos, docs, test updates, or minor internal changes/refactors)

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (f84ac2e) 100.00% compared to head (274e400) 100.00%.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #424   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           21        21           
  Lines         5942      5951    +9     
=========================================
+ Hits          5942      5951    +9     

Flag	Coverage Δ
py3.10	88.30% <100.00%> (+0.01%)	⬆️
py3.10_all	98.72% <100.00%> (+<0.01%)	⬆️
py3.10_pydantic1	48.29% <33.33%> (-0.03%)	⬇️
py3.10_pydantic2	48.02% <33.33%> (-0.03%)	⬇️
py3.10_types	98.72% <100.00%> (+<0.01%)	⬆️
py3.11	88.28% <100.00%> (+0.01%)	⬆️
py3.11_all	98.72% <100.00%> (+<0.01%)	⬆️
py3.11_types	98.72% <100.00%> (+<0.01%)	⬆️
py3.12	88.28% <100.00%> (+0.01%)	⬆️
py3.12_all	98.72% <100.00%> (+<0.01%)	⬆️
py3.12_types	98.72% <100.00%> (+<0.01%)	⬆️
py3.7	88.87% <100.00%> (+0.01%)	⬆️
py3.7_all	99.49% <100.00%> (+<0.01%)	⬆️
py3.7_types	99.47% <100.00%> (+<0.01%)	⬆️
py3.8	89.02% <100.00%> (+0.01%)	⬆️
py3.8_all	99.51% <100.00%> (+<0.01%)	⬆️
py3.8_types	99.49% <100.00%> (+<0.01%)	⬆️
py3.9	88.87% <100.00%> (+0.01%)	⬆️
py3.9_all	99.37% <100.00%> (+<0.01%)	⬆️
py3.9_types	99.37% <100.00%> (+<0.01%)	⬆️

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