A successful response will be an object of the form {
'ListID' => The id of the list
'Title' => The title of the list
'UnsubscribePage' => The page which subscribers are redirected to upon unsubscribing
'ConfirmedOptIn' => Whether the list is Double-Opt In
'ConfirmationSuccessPage' => The page which subscribers are
redirected to upon confirming their subscription
'UnsubscribeSetting' => The unsubscribe setting for the list. Will
be either CS_REST_LIST_UNSUBSCRIBE_SETTING_ALL_CLIENT_LISTS or
CS_REST_LIST_UNSUBSCRIBE_SETTING_ONLY_THIS_LIST.
}