TF-3752 Better error handling when updating recipients in Forwarding

Signed-off-by: dab246 <tdvu@linagora.com>

lib/features/manage_account/domain/exceptions/forward_exception.dart

@@ -1,5 +1,7 @@
 class NotFoundForwardException implements Exception {}
 
+class UpdateForwardException implements Exception {}
+
 class RecipientListIsEmptyException implements Exception {}
 
 class RecipientListWithInvalidEmailsException implements Exception {}