Adds a billing contact to your account and attaches it to one of your subscriptions. name is sanitized and split on its first space into a first and last name, and the contact is filed with the Billing Contact designation. The subscription's contact list is rewritten as its existing entries plus the primary contact plus the new one. A contact that is created but cannot be attached answers 400 even though the contact now exists. Requires an API key with the Admin role.