public static UserInput ui(Annotation a, String value) {
        return new UserInput(a, value);
    }
userInput with an annotation.
https://docs.vespa.ai/en/reference/query-language-reference.html#userinput

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