private String formatLiteral(String literal) {
        var escaped = GRAMMAR_LITERAL_ESCAPE_RE.matcher(literal).replaceAll(
                m -> GRAMMAR_LITERAL_ESCAPES.getOrDefault(m.group(0), m.group(0)));

        return "\"" + escaped + "\"";
    }
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