function lookup_consumer($consumer_key) {
function lookup_token($consumer, $token_type, $token) {
function lookup_nonce($consumer, $token, $nonce, $timestamp) {
function new_request_token($consumer, $callback = null) {
// return a new token attached to this consumer
function new_access_token($token, $consumer, $verifier = null) {
// return a new access token attached to this consumer
// for the user associated with this token if the request token
// should also invalidate the request token