function ensureString(o) {
    if (Buffer.isBuffer(o)) {
        return o.toString();
    } else if (typeof o === "object") {
        return JSON.stringify(o);
    } else if (typeof o === "string") {
        return o;
    }
    return ""+o;
}
Converts the provided argument to a String, using type-dependent
methods.

@param  {any}    o - the property to convert to a String
@return {String} the stringified version
@memberof @node-red/util_util