The CREATE path hardcoded relationTargetFieldMetadataUniversalIdentifier
to null while passing the FK id through. The migration system's
resolveUniversalRelationIdentifiersToIds then renormalises by treating
the null universal identifier as authoritative and nullifying the FK id,
silently dropping the relation traversal on save.
Mirror the UPDATE path: include relationTargetFieldMetadataId in the
foreignKeyValues passed to resolveEntityRelationUniversalIdentifiers and
read the resolved universal identifier from its result.
Félix Malfait
2bd03cab91