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 {}

lib/features/manage_account/domain/model/add_recipients_in_forwarding_request.dart

@@ -11,11 +11,14 @@ class AddRecipientInForwardingRequest with EquatableMixin {
   });
 
   TMailForward get newTMailForward {
-    final newListRecipients = currentForward.forwards
-        .where((recipient) => !listRecipientAdded.contains(recipient))
-        .toSet();
-    newListRecipients.addAll(listRecipientAdded);
-    return currentForward.copyWith(forwards: newListRecipients);
+    final currentRecipients = currentForward.forwards ?? {};
+
+    final updatedRecipients = {
+      ...currentRecipients,
+      ...listRecipientAdded,
+    };
+
+    return currentForward.copyWith(forwards: updatedRecipients);
   }
 
   @override

lib/features/manage_account/domain/model/delete_recipient_in_forwarding_request.dart

@@ -11,11 +11,11 @@ class DeleteRecipientInForwardingRequest with EquatableMixin {
   });
 
   TMailForward get newTMailForward {
-    final newListRecipients = currentForward.forwards
-        .where((recipient) => !listRecipientDeleted.contains(recipient))
-        .toSet();
+    final currentRecipients = currentForward.forwards ?? {};
 
-    return currentForward.copyWith(forwards: newListRecipients);
+    final updatedRecipients = currentRecipients.difference(listRecipientDeleted.toSet());
+
+    return currentForward.copyWith(forwards: updatedRecipients);
   }
 
   @override