chore: Add Pydantic mypy plugin

[jdeschamps]

We have been using mypy and Pydantic together wrong. This PR will require some additional mypy fixing.

https://docs.pydantic.dev/latest/integrations/mypy/#enabling-the-plugin

Description

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Changes Made

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Breaking changes

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Please ensure your PR meets the following requirements:

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.57%. Comparing base (929b9b8) to head (243d552).
Report is 15 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #254      +/-   ##
==========================================
+ Coverage   87.20%   87.57%   +0.36%     
==========================================
  Files         131      135       +4     
  Lines        4956     4950       -6     
==========================================
+ Hits         4322     4335      +13     
+ Misses        634      615      -19     

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