Allow nanosecond precision in NeTEx date times

[leonardehrenfried]

Summary

In #7956 we noticed that NeTEx date times with sub-millisecond precision would silently be converted to null, which would fail the parsing of an Italian NeTEx feed with data like this:

<UicOperatingPeriod
	xmlns="http://www.netex.org.uk/netex"
	xmlns:ns2="http://www.opengis.net/gml/3.2"
	xmlns:ns3="http://www.siri.org.uk/siri" version="153" id="IT:ITH4:UicOperatingPeriod:U182_20260416_0">
	<FromDate>2026-05-03T23:30:09.398629+02:00</FromDate>
	<ToDate>2026-08-31T00:00:00</ToDate>
	<ValidDayBits>111111011111101111110111111010111101111100111110011111001111100111110011111001111100111110011111001111100111110011111001</ValidDayBits>
</UicOperatingPeriod>

entur/netex-java-model#298 in the upstream library fixes the issue.

BTW, I'm not saying that this is good data - it is very ambiguous, but that is a separate issue.

Issue

noi-techpark/opendatahub-mentor-otp#330

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.59%. Comparing base (02c0b4b) to head (252358b).
⚠️ Report is 16 commits behind head on dev-2.x.

Additional details and impacted files

@@            Coverage Diff             @@
##             dev-2.x    #7983   +/-   ##
==========================================
  Coverage      74.58%   74.59%           
- Complexity     22615    22618    +3     
==========================================
  Files           2503     2503           
  Lines          87668    87668           
  Branches        8665     8665           
==========================================
+ Hits           65389    65392    +3     
+ Misses         19240    19239    -1     
+ Partials        3039     3037    -2     

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