add minimum requirement for MinBackOffDuration

Author: zhiyuanliang-ms

src/Microsoft.Extensions.Configuration.AzureAppConfiguration/AzureAppConfigurationProvider.cs

@@ -137,6 +137,13 @@ public AzureAppConfigurationProvider(IConfigurationClientManager configClientMan
                 MinRefreshInterval = RefreshConstants.DefaultRefreshInterval;
             }
 
+            if (options.MinBackoffDuration < TimeSpan.FromSeconds(1))
+            {
+                throw new ArgumentException(
+                    $"{nameof(options.MinBackoffDuration)} must be at least 1 second",
+                    nameof(options));
+            }
+
             // Enable request tracing if not opt-out
             string requestTracingDisabled = null;
             try