Add DeviceNotOnline to error codes (#3450)

Co-authored-by: Preben Huybrechts <preben.huybrechts@niko.eu>

Author: timtay-microsoft

iothub/service/src/Common/Exceptions/ErrorCode.cs

@@ -205,6 +205,14 @@ public enum ErrorCode
         [EditorBrowsable(EditorBrowsableState.Never)]
         JobNotFound = 404002,
 
+        /// <summary>
+        /// The operation failed because the device is offline or the direct method callback isn't registered.
+        /// <para>
+        /// For more information, see <see href="https://aka.ms/iothub404103">404103 Device not online</see>.
+        /// </para>
+        /// </summary>
+        DeviceNotOnline = 404103,
+
         /// <summary>
         /// The error is internal to IoT hub and is likely transient.
         /// <para>

iothub/service/tests/ExceptionHandlingHelperTests.cs

@@ -33,6 +33,25 @@ public async Task GetExceptionCodeAsync_ContentAndHeadersMatch_ValidErrorCode()
             Assert.AreEqual(ErrorCode.DeviceNotFound, errorCode);
         }
 
+        [TestMethod]
+        public async Task GetExceptionCodeAsync_ContentAndHeadersMatch_ValidErrorCode_DeviceNotOnline()
+        {
+            // arrange
+            var httpResponseMessage = new HttpResponseMessage(System.Net.HttpStatusCode.BadRequest);
+            var exceptionResult = new IoTHubExceptionResult
+            {
+                Message = "{\"errorCode\":404103}"
+            };
+            httpResponseMessage.Content = new StringContent(JsonConvert.SerializeObject(exceptionResult));
+            httpResponseMessage.Headers.Add(CommonConstants.HttpErrorCodeName, "DeviceNotOnline");
+
+            // act
+            ErrorCode errorCode = await ExceptionHandlingHelper.GetExceptionCodeAsync(httpResponseMessage);
+
+            // assert
+            Assert.AreEqual(ErrorCode.DeviceNotOnline, errorCode);
+        }
+
         [TestMethod]
         public async Task GetExceptionCodeAsync_ContentAndHeadersMisMatch_InvalidErrorCode()
         {