public async Task <IActionResult> GetDataPoint(
            DateTime datePoint,
            string currency = null
            )
        {
            Console.WriteLine("Requested data on {0:yyyy-MM-dd}", datePoint);
            var data = await GetFilteredDataSet();

            var point = data.FirstOrDefault(c => c.Date == datePoint);

            if (point == null)
            {
                point = await _currencyManager.FetchPoint(datePoint, currency);

                if (point == null)
                {
                    return(NotFound(_currencyManager.Error));
                }
            }

            return(Ok(point));
        }