The MIME type used in the JSON-LD serializer should be application/ld+json

[Alfiva]

The MIME type used in org.universAAL.middleware.serialization.json.JSONLDSerialization to identify the serializer and diferentiate it from the Turtle one is now defined as "application/json".
That one is officially for JSON alone. Instead, for JSON-LD we should use "application/ld+json" (see https://en.wikipedia.org/wiki/JSON-LD)