fixing some security issues and harderning service

app-code/plugins/auth.php

@@ -2,10 +2,16 @@
 /*
 This file can be installed in any service. If done so a user can authenticate with Jakach Auth. Jakach Auth will redirect the user here where their token gets validated, and then they can be logged in to your service.
 */
-$auth_token = $_GET["auth"];
+$auth_token = $_GET["auth"] ?? "";
+header('Content-Type: application/json');
+
+if ($auth_token === '') {
+    echo json_encode(['status' => 'failure', 'msg' => 'Missing auth token']);
+    exit;
+}
 
 // Check the auth token against Jakach login API
-$check_url = "https://auth.jakach.ch/api/auth/check_auth_key.php?auth_token=" . $auth_token;
+$check_url = "https://auth.jakach.ch/api/auth/check_auth_key.php?auth_token=" . rawurlencode($auth_token);
 
 // Initialize cURL
 $ch = curl_init();
@@ -47,4 +53,3 @@ if (isset($data['status'])) {
     echo json_encode(['status' => 'failure', 'msg' => 'Invalid response from authentication server']);
 }
 ?>
-