fix: #351 make serde errors more informative

[adawang1210]

Summary

Serializing state that contains a pandas DataFrame without configuring pandas_kwargs failed with an opaque internal error (TypeError: serialize_pandas_df() missing 1 required positional argument: 'pandas_kwargs', or KeyError: 'path' if path was missing). There was also no way to tell which state field failed. Serde failures now raise clear, actionable errors.

Before:

TypeError: serialize_pandas_df() missing 1 required positional argument: 'pandas_kwargs'

After:

ValueError: Failed to serialize state field 'output' (value of type DataFrame): Serializing a pandas
DataFrame requires a `path` entry in `pandas_kwargs` -- this is the base path where the dataframe is
saved as a parquet file. Pass it through whatever triggers serialization, e.g.
`LocalTrackingClient(..., serde_kwargs={"pandas_kwargs": {"path": "/some/dir"}})` or
`state.serialize(pandas_kwargs={"path": "/some/dir"})`. Got pandas_kwargs=None.

Related issue

Addresses the "make it clear if we do not have the values we need" and "type-check the values coming in" parts of #351.

Changes made

• burr/integrations/serde/pandas.py: pandas_kwargs is now optional in the signature; the serializer validates it and raises an informative ValueError when path is missing; the deserializer no longer requires pandas_kwargs at all (the parquet path is embedded in the serialized value).
• burr/core/state.py: State.serialize / State.deserialize wrap serde failures with the offending field name (chained with from e so the original traceback is preserved).
• burr/core/serde.py: unknown deserializer keys now report the registered keys and hint that the registering module may not have been imported.
• tests/core/test_serde.py, tests/integrations/serde/test_pandas.py: cover the missing-kwargs, missing-path, unknown-key, and kwargs-free deserialization cases.

How to test

pytest tests/core/test_serde.py tests/integrations/serde/test_pandas.py

Checklist

• Tests added or updated
• All tests pass locally (pytest tests/ --ignore=tests/integration_tests: 577 passed, 5 skipped)
• Commits signed off (git commit -s)
• Pre-commit hooks pass (black, isort, flake8)
• CONTRIBUTING.md guidelines followed

[elijahbenizzy]

This seesms reasonable