source-impact-native: support millisecond datetime parsing in _s_to_dt function

[SeanWhelan]

Description:

Fix source-impact-native cursor parsing to accept timestamps with fractional seconds. The Impact API's Tasks endpoint returns CreationDate values like 2024-07-17T21:55:46.000+0000, which _s_to_dt could not parse because its strptime format string (%Y-%m-%dT%H:%M:%S%z) had no .%f component. The helper now tries the fractional-second format first and falls back to the original, raising a clear ValueError if neither matches. Other Impact endpoints that omit fractional seconds continue to parse as before.

Workflow steps:

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Documentation links affected:

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Notes for reviewers:

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[Alex-Bair]

LGTM % a potential simplification

[Alex-Bair]

If these strings are always in ISO 8601 format (which seems to be true based off the two formats here?), this could be simplified with datetime.fromisoformat:

Suggested change

	def _s_to_dt(date: str):
	date = datetime.strptime(date, "%Y-%m-%dT%H:%M:%S%z")
	return date
	for fmt in ("%Y-%m-%dT%H:%M:%S.%f%z", "%Y-%m-%dT%H:%M:%S%z"):
	try:
	return datetime.strptime(date, fmt)
	except ValueError:
	continue
	raise ValueError(f"unrecognized datetime format: {date}")
	def _s_to_dt(date: str) -> datetime:
	return datetime.fromisoformat(date)