MDL-70264 badges: remove badges/oauth2callback.php

File badges/oauth2callback.php has been removed and now badges
API will use admin/oauth2callback.php because it makes no sense having
it twice.

Credits go to Andrew Nicols for raising it!

badges/classes/oauth2/client.php

@@ -173,7 +173,7 @@ class client extends \core\oauth2\client {
      * @return moodle_url url of callback
      */
     public static function callback_url() {
-        return new moodle_url('/badges/oauth2callback.php');
+        return new moodle_url('/admin/oauth2callback.php');
     }
 
     /**

badges/oauth2callback.php

@@ -1,57 +0,0 @@
-<?php
-// This file is part of Moodle - http://moodle.org/
-//
-// Moodle is free software: you can redistribute it and/or modify
-// it under the terms of the GNU General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// Moodle is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-// GNU General Public License for more details.
-//
-// You should have received a copy of the GNU General Public License
-// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
-
-/**
- * Verify authorization callback.
- *
- * @package    core_badges
- * @copyright  2020 Tung Thai
- * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
- * @author     Tung Thai <[email protected]>
- */
-require_once(__DIR__ . '/../config.php');
-
-$error = optional_param('error', '', PARAM_RAW);
-
-if ($error) {
-    $message = optional_param('error_description', '', PARAM_RAW);
-    if ($message) {
-        print_error($message);
-    } else {
-        print_error($error);
-    }
-    die();
-}
-
-require_login();
-
-// The authorization code generated by the authorization server.
-$code = required_param('code', PARAM_RAW);
-$scope = required_param('scope', PARAM_RAW);
-
-// The state parameter we've given (used in moodle as a redirect url).
-$state = required_param('state', PARAM_LOCALURL);
-
-$redirecturl = new moodle_url($state);
-$params = $redirecturl->params();
-
-if (isset($params['sesskey']) and confirm_sesskey($params['sesskey'])) {
-    $redirecturl->param('oauth2code', $code);
-    $redirecturl->param('scope', $scope);
-    redirect($redirecturl);
-} else {
-    print_error('invalidsesskey');
-}