TF-1897 Implement resend sending email when failed

(cherry picked from commit f508b65688503e9ae8ece5a1924e84481b98a39e)

lib/features/sending_queue/domain/model/sending_email.dart

@@ -101,6 +101,10 @@ class SendingEmail with EquatableMixin {
 
   bool get isWaiting => sendingState == SendingState.waiting;
 
+  bool get isError => sendingState == SendingState.error;
+
+  bool get isSuccess => sendingState == SendingState.success;
+
   @override
   List<Object?> get props => [
     sendingId,