Support multiple room sizes via room_groups table

schema.sql

@@ -11,11 +11,19 @@ END $$;
 CREATE TABLE IF NOT EXISTS trips (
     id BIGSERIAL PRIMARY KEY,
     name TEXT NOT NULL,
-    room_size INTEGER NOT NULL DEFAULT 2,
     prefer_not_multiple INTEGER NOT NULL DEFAULT 5,
     no_prefer_cost INTEGER NOT NULL DEFAULT 10
 );
 
+CREATE TABLE IF NOT EXISTS room_groups (
+    id BIGSERIAL PRIMARY KEY,
+    trip_id BIGINT NOT NULL REFERENCES trips(id) ON DELETE CASCADE,
+    size INTEGER NOT NULL,
+    count INTEGER NOT NULL,
+    CHECK(size >= 1),
+    CHECK(count >= 1)
+);
+
 CREATE TABLE IF NOT EXISTS trip_admins (
     id BIGSERIAL PRIMARY KEY,
     trip_id BIGINT NOT NULL REFERENCES trips(id) ON DELETE CASCADE,