Fix: days_to_expiration sent under wrong query param name (dte)

[MarketDataDev03]

Fix: days_to_expiration sent under wrong query param name (dte)

Closes #30

Summary

The days_to_expiration filter on client.options.chain(...) was silently
ignored by the API. The URL builder serializes input models with
by_alias=True (src/marketdata/resources/base.py:45), but the
days_to_expiration field had no Pydantic alias, so it was emitted to the
wire under its Python name (days_to_expiration=30) instead of the parameter
the API expects (dte=30). The backend doesn't recognize that key, so the
filter was dropped without error and the full chain was returned.

client.options.chain(symbol="AAPL", days_to_expiration=30)
# before: ...?days_to_expiration=30   -> ignored by API
# after:  ...?dte=30                  -> filter applied

Changes

1. The fix — src/marketdata/input_types/options.py

Added alias="dte" to the days_to_expiration field, matching the existing
convention used by every other renamed field in the model (strikeLimit,
minBid, from/to, etc.). Because BaseModelConfig sets
populate_by_name=True, callers keep using days_to_expiration=... while the
emitted query parameter is now dte.

2. Targeted regression test — src/tests/test_options_chain.py

test_options_chain_input_days_to_expiration_alias_on_wire asserts that a real
request carries dte=30 on the wire and never days_to_expiration, mirroring
the existing from_date/to_date alias test.

3. Preventive test for the whole bug class — src/tests/test_input_types.py

A parametrized test (test_snake_case_input_fields_have_api_alias)
auto-discovers every BaseInputType model in the SDK and asserts that any field
whose Python name contains an underscore is sent under an explicit alias
(or is exempt via GLOBAL_EXCLUDED_PARAMS, like output_format/filename,
which never reach the query string). A guard test ensures discovery isn't
silently empty. This catches the next field that forgets its alias, not just
this one.

Audit

I audited every input model across options.py, funds.py, markets.py,
stocks.py, and base.py. days_to_expiration was the only field missing
an alias — all other renamed fields (strike_limit, min_bid/max_bid,
min_ask/max_ask, max_bid_ask_spread[_pct], min_open_interest,
min_volume, from_date/to_date, use_52_week, adjust_splits,
report_type, date_format, add_headers, use_human_readable) already
carry the correct alias. The new preventive test now enforces this invariant.

Testing

• Verified the new alias test fails when the alias="dte" fix is reverted,
  confirming it isn't a false green.
• Full suite: 328 passed.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (fb1ea8e) to head (b101f92).

Additional details and impacted files

@@            Coverage Diff            @@
##              main       #31   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files           52        52           
  Lines         2281      2281           
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  Hits          2281      2281           

Flag	Coverage Δ
unittests	100.00% <ø> (ø)

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