Authentication fix for getting a REST gateway access token (thephpleague#201)

Author: vdbelt

src/Message/RestTokenRequest.php

@@ -36,7 +36,7 @@ public function sendData($data)
             $this->getEndpoint(),
             array(
                 'Accept' => 'application/json',
-                'Authorization' => 'Bearer ' . base64_encode("{$this->getClientId()}:{$this->getSecret()}"),
+                'Authorization' => 'Basic ' . base64_encode("{$this->getClientId()}:{$this->getSecret()}"),
             ),
             $body
         );