[teppope]

Summary

• SiteFrameParser no longer throws a NullPointerException when a Parking has no ParentSiteRef.
• The parser adds every Parking to the parking index. It adds a Parking to the index by parent site only when the Parking has a ParentSiteRef.

Issue

The NeTEx Nordic profile makes ParentSiteRef optional on a Parking. A file with a standalone Parking stopped the whole parse. The Parking example for a park-and-ride proposal on entur/profile-examples has no ParentSiteRef, and the parser could not read it.

Verification

• ✅ Nordic NeTEx Profile: the stops document, Site, gives ParentSiteRef the cardinality 0:1. Parking inherits it from Site.
• ✅ New test SiteFrameParserTest fails without the fix: NullPointerException: Cannot invoke "SiteRefStructure.getRef()" because the return value of "Parking.getParentSiteRef()" is null, at SiteFrameParser.parseParkings.
• ✅ With the fix, the test passes. mvn verify -P prettierCheck passes, with 36 tests.