I am using a Salesforce upsert operation in a process and would like to set a field in an object to null (the field may have an existing value). How do I achieve this using the Salesforce conector? I knpw accessing the Salesforce API directly (e.g. through soapUI) I can use the fieldsToNull element to provide a list of fiels I want to set to null. How is this achieved usng the Boomi Salesforce connector?