How do I set a column to be unique in drizzle syntax for mySQL?

export const authUsers = mysqlTable(
    'auth_users',
    {
        id: varchar('id', { length: 191 }).primaryKey().notNull(),
        username: varchar('username', { length: 191 }).notNull()
    },
    (table) => {
        return {
            idKey: uniqueIndex('auth_users_id_key').on(table.id),
            usernameKey: uniqueIndex('auth_users_username_key').on(table.username)
        };
    }
);