open method
Implementation
@override
Future<Database> open() async {
  sqfliteFfiInit();
  final databaseFactory = databaseFactoryFfi;
  return databaseFactory.openDatabase(
    await getDbFullName(),
    options: SqfliteOpenDatabaseOptions(
      onCreate: onDbCreate,
      onUpgrade: onDbUpgrade,
      onDowngrade: onDbDowngrade,
      version: dbVersion,
    ),
  );
}