Remove an item line from an ASN via to API

When modifying an existing ASN via the API, we are unable to remove an item line.

We are using the "POST /api/ASN/{id}" request and are able to modify all the single fields. We can also add new Items, or modify the quantity, etc. for existing items. However we can't find any way to remove an item line: leaving the line out of the Items array or setting the Quantity to 0 just leaves the line unmodified.

Can you please tell us how we would remove an item line from an ASN via the API.

Another undesirable behaviour we've found is that the POST request has include the ClientId, otherwise we get an error 500. This seems strange since the ClientId is not required when creating the ASN with the PUT request (since we have a single client account). Seems that the ClientId should also be assumed for the POST request, otherwise we have to make another API call to retrieve the ClientId (since we don't store this in our system).