Update for python 3.9

[hmvp]

Also added some more testing around domain models

[codecov-commenter]

Codecov Report

Merging #13 (90fc471) into main (706ef48) will increase coverage by 0.36%.
The diff coverage is 76.92%.

@@            Coverage Diff             @@
##             main      #13      +/-   ##
==========================================
+ Coverage   80.95%   81.31%   +0.36%     
==========================================
  Files          84       84              
  Lines        4531     4534       +3     
  Branches      559      559              
==========================================
+ Hits         3668     3687      +19     
+ Misses        711      701      -10     
+ Partials      152      146       -6     

Impacted Files	Coverage Δ
orchestrator/domain/base.py	75.42% <61.53%> (+3.47%)	⬆️
orchestrator/types.py	97.61% <90.00%> (+0.02%)	⬆️
orchestrator/__init__.py	100.00% <100.00%> (ø)
orchestrator/utils/state.py	92.78% <100.00%> (+0.07%)	⬆️
orchestrator/utils/docs.py	82.43% <0.00%> (+2.70%)	⬆️

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[acidjunk]

The new pydantic typing functions improve readability a lot. Great.