Returns the timestamp formatted as a string in extended timezone-qualified ISO format. If the timezone offset is 0, the format is yyyy-mm-ddThh:mm:ss.uuuuuuZ. If the offset is positive, the string is formatted as yyyy-mm-ddThh:mm:ss.uuuuuu+hh:mm. If the offset is negative, the result will be in the format yyyy-mm-ddThh:mm:ss.uuuuuu-hh:mm.