public async Task UpdateSubscription(int id, CreateOrUpdateSubscriptionRequest request)
        {
            if (request.Price <= 0 || request.Time <= 0)
            {
                throw new ArgumentException();
            }
            var sub = await context.Subscriptions.FindAsync(id);

            sub.Name  = request.Name;
            sub.Price = request.Price;
            sub.Time  = request.Time;
            await context.SaveChangesAsync();
        }
        public async Task AddSubscription(CreateOrUpdateSubscriptionRequest request)
        {
            if (request.Price <= 0 || request.Time <= 0)
            {
                throw new ArgumentException();
            }
            var sub = new Subscription {
                Name  = request.Name,
                Price = request.Price,
                Time  = request.Time
            };
            await context.Subscriptions.AddAsync(sub);

            await context.SaveChangesAsync();
        }