renderJson
Serialize a UDM value to a JSON string. See Chapter 24.
value(required): UDM value to serializepretty(optional, default false): pretty-print with indentation
utlx
renderJson({name: "Alice", age: 30}) // '{"name":"Alice","age":30}'
renderJson({name: "Alice", age: 30}, true) // pretty-printed with newlines