osu: [Big!] rework load_beatmap so that it can retrieve beatmapsets

Also
- scoreboard can handle beatmapsets now
- "when" column is included
- beatmapWithMode's mode field is now optional

youmubot-db-sql/migrations/20250220161301_make_last_beatmap_mode_nullable.sql

@@ -0,0 +1,6 @@
+-- Add migration script here
+
+ALTER TABLE osu_last_beatmaps RENAME COLUMN mode TO mode_old;
+ALTER TABLE osu_last_beatmaps ADD COLUMN mode INT NULL;
+UPDATE osu_last_beatmaps SET mode = mode_old;
+ALTER TABLE osu_last_beatmaps DROP COLUMN mode_old;

youmubot-db-sql/src/models/osu.rs

@@ -3,7 +3,7 @@ use crate::models::*;
 pub struct LastBeatmap {
     pub channel_id: i64,
     pub beatmap: Vec<u8>,
-    pub mode: u8,
+    pub mode: Option<u8>,
 }
 
 impl LastBeatmap {