Add room assignment solver with prefer_not_multiple setting

schema.sql

@@ -10,11 +10,11 @@ END $$;
 
 CREATE TABLE IF NOT EXISTS trips (
     id BIGSERIAL PRIMARY KEY,
-    name TEXT NOT NULL
+    name TEXT NOT NULL,
+    room_size INTEGER NOT NULL DEFAULT 2,
+    prefer_not_multiple INTEGER NOT NULL DEFAULT 5
 );
 
-ALTER TABLE trips ADD COLUMN IF NOT EXISTS room_size INTEGER NOT NULL DEFAULT 2;
-
 CREATE TABLE IF NOT EXISTS trip_admins (
     id BIGSERIAL PRIMARY KEY,
     trip_id BIGINT NOT NULL REFERENCES trips(id) ON DELETE CASCADE,