MDL-33507 - oauth2lib: switch 'code' to oauth2code

To avoid param collisions in future.

admin/oauth2callback.php

@@ -39,7 +39,7 @@ $redirecturl = new moodle_url($state);
 $params = $redirecturl->params();
 
 if (isset($params['sesskey']) and confirm_sesskey($params['sesskey'])) {
-    $redirecturl->param('code', $code);
+    $redirecturl->param('oauth2code', $code);
     redirect($redirecturl);
 } else {
     print_error('invalidsesskey');

lib/oauthlib.php

@@ -425,7 +425,7 @@ abstract class oauth2_client extends curl {
 
         // If we've been passed then authorization code generated by the
         // authorization server try and upgrade the token to an access token.
-        $code = optional_param('code', null, PARAM_RAW);
+        $code = optional_param('oauth2code', null, PARAM_RAW);
         if ($code && $this->upgrade_token($code)) {
             return true;
         }