unable to add form fields to an unclaimed draft

[erosiec]

Form fields are not recognized when used in a request to /v3/unclaimed_draft/create

The request does not fail, but when the document is opened using the claim URL, none of the specified fields appear on the document.

tested with:

var draft = new SignatureRequest();
draft.AddFile("doc2.pdf").WithFields(
        new FormField("datefield", FormField.TypeText, 1, 140, 72, 36, 36, true, 0, "numbers_only")
);
draft.TestMode = true;
var response = client.CreateUnclaimedDraft(draft, UnclaimedDraft.Type.RequestSignature);