I noticed in the UI that when I try to insert a contact with an e-mail address that a lead already has, I get a warning (before I click save and insert the contact) saying that this is a possible duplicate. However, I am still able to save the contact ignoring the warning. This is something that I often want to happen. But I can't seem to find anything in the docs that offers a way to force the operation when I'm inserting the same contact with the REST API. What seems to be a warning in the UI is an error in the REST API. Is there a way (in the REST API) to ignore this error and insert the contact anyway? It certainly seems possible when done manually through the UI.