Fix pydantic deserialization issues with root obj

[munrojm]

This PR converts pydantic deserialization calls to use dict(model) instead of model.model_dump() to avoid some edge cases with root level instantiated python objects being partially de-serialized.

Note this is not an issue in pydantic v1.

[codecov-commenter]

Codecov Report

All modified lines are covered by tests ✅

Comparison is base (83b27a0) 70.42% compared to head (cafa16a) 70.42%.
Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #854   +/-   ##
=======================================
  Coverage   70.42%   70.42%           
=======================================
  Files          51       51           
  Lines        2482     2482           
=======================================
  Hits         1748     1748           
  Misses        734      734           

Files	Coverage Δ
mp_api/client/core/client.py	82.87% <100.00%> (ø)

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.