primary label fails to sort when specified using ldpath

[elrayle]

Description

Language processing in QA requires language tagged RDF::Literals. Without that, the sorting process is not able to sort by language and within language. Currently, the ldpath_service using the ldpath gem converts Literals to Strings.

See PR samvera-labs/ldpath#18 which adds the option to have ldpath return Literals.

Expected

When a config specifies an ldpath for the primary label, the label values will be sorted by language.

Actual

When a config specifies an ldpath for the primary label, the label values are not sorted by language.

Reproduce

Update the fixtures used by the language sorting tests (i.e. /spec/fixtures/authorities/linked_data/lod_lang*) to only use ldpath instead of predicates.

This will cause multiple tests to fail.