Reference of v4 song random

arguments	description	optional
start	range of start	YES when `end` is not passed in
end	range of end	YES

Explain

Roll a song from a given difficulty range.

The default range is 2 to 23.
For easier storage and higher compatibility,
We make the song rating table from

1 2 3 4 5 6 7 8 9 9+ 10 10+ 11

expanded to

1 1+ 2 2+ 3 3+ 4 4+ 5 5+ 6 6+ 7 7+ 8 8+ 9 9+ 10 10+ 11 11+

So the algorithm is (ratingNumber * 2) + (ratingPlus ? 1 : 0)
As you can see, now the range is 2 to 23.
We removed the full song info output feature in this version.
Make it clean and dry. If you want to get the song info in the same request, Please reference the batch api.

{
    "status": 0,
    "content": {
        "id": "ifi",
        "rating_class": 2
    }
}