async getMostRecentlyPublishedPostDate() {
        const result = await this.#db.knex.select('published_at')
            .from('posts')
            .whereIn('status', ['sent', 'published'])
            .orderBy('published_at', 'desc')
            .limit(1);

        return result?.[0]?.published_at ? new Date(result?.[0]?.published_at) : null;
    }
Returns the most recently `published_at` post that was published or sent
via email