Imports a collection of contacts. Creates contacts if they do not exist and updates contacts if they do. This is an async operation and you will need to check when it is complete by calling getImportStatus
Note: It isn't possible to specify the value for the contactId field when creating a contact, so it is only used to check for a matching contact when specified
This call will be enabled in the unified contacts public preview as soon as possible. Remember you will need to have opted into the public preview in order to access this service.