private async static Task <string> AddNewSubscriptionAndGetName(string mail, string number, int?diffPercent, int?diffPln)
        {
            using SqlConnection conn = ConnectionFactory.CreateConnection();
            conn.Open();
            Subscriber subscriber = DbUtilities.GetOrCreateSubscriber(conn, mail);
            LegoSet    set        = await DbUtilities.GetOrCreateSet(conn, int.Parse(number));

            Subscription subscription = CreateSubscription(subscriber, set, diffPercent, diffPln);

            DbUtilities.CreateOrUpdateSubscriptionInDb(conn, subscription);

            return(set.Name);
        }