we use your forms api to send data from our website to HubSpot. Previously we used the "standard" forms api and had a field where we would not overwrite the property of a contact (if it already existed) but update it (by appending a semi-colon ; before the value). This worked just fine. But since we updated to the new ajax version of the forms api, this doesn't seem to work anymore, the property gets overwritten. Is there a new way to update a property or are we doing something wrong?