/**
 * A factory function that will return a function, bound to a closure that holds an id property.
 * Each time you call the function, it will decrement the id and return it to you. We decrement it
 * so we are sure it never matches a traditional database key
 *
 * @return {function(): number}
 */
export default function() {
    let id = 0;
    return function() {
        id--;
        return id;
    }
}