public Optional<String> maybeVisit(JsonNode schema, String baseName, String name) {
            if (schema.has("const")) {
                var rule = addRule(name, generateConstant(schema.get("const")) + " space");
                return Optional.of(rule);
            }

            return Optional.empty();
        }
Converts a JSON Schema to a GBNF grammar to be used for structured output with llama.cpp.
It is a port of Python implementation from llama.cpp repository.
Current implementation doesn't support regex patterns, resolving $ref or fetching schemas from URLs.
The plan is to replace this with C++ implementation from llama.cpp though JNI.
model-integration/src/main/java/ai/vespa/llm/clients/JsonSchemaToGrammar.java