Improve context caching
The Titanium JSON-LD library can do context caching. See: https://github.com/filip26/titanium-json-ld/blob/main/src/main/java/com/apicatalog/jsonld/JsonLdOptions.java#L118
This is cleaner than the current solution, but we need to figure out how to configure the JsonLdOptions when Titanium is called by Jena.