Multiple meeting lobbies and beta-gated features (3.5.2)

- /meeting add-lobby, remove-lobby, lobbies: up to 10 lobbies per server, capped in the database
- Deleted voice channels are dropped from the lobbies
- Beta features: registered only in the beta server and usable only with the Beta Tester role (BETA_GUILD_ID, BETA_ROLE_ID); fails closed
- /beta (bot owner only) shows how beta access is set up

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>

schema.sql

@@ -73,6 +73,33 @@ CREATE TABLE IF NOT EXISTS meeting_settings (
     lobby_channel_id BIGINT
 );
 
+-- A server can have several lobbies (at most 10; the trigger enforces it, and
+-- is the same as the API's migration 000020). meeting_settings.lobby_channel_id
+-- is the old single-lobby column, no longer read.
+CREATE TABLE IF NOT EXISTS meeting_lobbies (
+    guild_id BIGINT NOT NULL,
+    channel_id BIGINT NOT NULL,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    PRIMARY KEY (guild_id, channel_id)
+);
+
+CREATE OR REPLACE FUNCTION meeting_lobbies_limit() RETURNS trigger AS $$
+BEGIN
+    PERFORM pg_advisory_xact_lock(NEW.guild_id);
+    IF EXISTS (SELECT 1 FROM meeting_lobbies WHERE guild_id = NEW.guild_id AND channel_id = NEW.channel_id) THEN
+        RETURN NEW;
+    END IF;
+    IF (SELECT COUNT(*) FROM meeting_lobbies WHERE guild_id = NEW.guild_id) >= 10 THEN
+        RAISE EXCEPTION 'a server can have at most 10 lobby channels' USING ERRCODE = '54000';
+    END IF;
+    RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;
+
+DROP TRIGGER IF EXISTS meeting_lobbies_limit ON meeting_lobbies;
+CREATE TRIGGER meeting_lobbies_limit BEFORE INSERT ON meeting_lobbies
+    FOR EACH ROW EXECUTE FUNCTION meeting_lobbies_limit();
+
 CREATE TABLE IF NOT EXISTS meeting_temp_channels (
     guild_id BIGINT NOT NULL,
     channel_id BIGINT NOT NULL,