fix: [#6861]TeamsSSOTokenExchangeMiddleware.DeduplicatedTokenExchange…

…IdAsync fails on BlobStorage ETag validation (#6867)

* add catch to capture 412 error in BlobsStorage

* use HttpStatusCode

libraries/Microsoft.Bot.Builder.Azure.Blobs/BlobsStorage.cs

@@ -290,6 +290,11 @@ internal BlobsStorage(BlobContainerClient containerClient, JsonSerializer jsonSe
                         $"An error occurred while trying to write an object. The underlying '{BlobErrorCode.InvalidBlockList}' error is commonly caused due to concurrently uploading an object larger than 128MB in size.",
                         ex);
                 }
+                catch (RequestFailedException ex)
+                when (ex.Status == (int)HttpStatusCode.PreconditionFailed)
+                {
+                    throw new InvalidOperationException($"Etag conflict: {ex.Message}");
+                }
             }
         }