public async Task <ActionResult> GetByPage(int page)
        {
            var clientsTask = _customersService.GetItemsPerPage(page);
            var countTask   = _customersService.Count();

            await Task.WhenAll(clientsTask, countTask);

            return(Ok(new
            {
                Items = clientsTask.Result,
                Count = countTask.Result
            }));
        }