public static UserInput ui(String index, String value) {
        return ui(A.defaultIndex(index), value);
    }
A convenience method to generate userInput with default index annotation.
https://docs.vespa.ai/en/reference/query-language-reference.html#userinput

@param index the index
@param value the value
@return the user input query
client/src/main/java/ai/vespa/client/dsl/Q.java