[BugFix] `__fields__` is deprecated, use `model_fields` instead

[deeleeramone]

1. Why?:

   • Instances where Pydantic syntax has not been updated for V2.

PydanticDeprecatedSince20: The `__fields__` attribute is deprecated, use `model_fields` instead. Deprecated in Pydantic V2.0 to be removed in V3.0. See Pydantic V2 Migration Guide at https://errors.pydantic.dev/2.8/migration/

- Warning is raised when using `pytest` with provider fetchers.

2. What?:

   • Use model_fields instead of __fields__.
     • fetcher.py
     • commands.py

3. Impact:

   • Resolves the warning.

4. Testing Done:

   • Recording a provider fetcher test, warning no longer being broadcast.