async getSlugUrl() {
        let url;
        while (!url || await this.#linkRedirectRepository.getByURL(url)) {
            const slug = crypto.randomBytes(4).toString('hex');
            url = new URL(`${this.#redirectURLPrefix}${slug}`, this.#baseURL);
        }
        return url;
    }
Get a unique URL with slug for creating unique redirects

@returns {Promise<URL>}