Issue CollaboraOnline#56: The CoolJwt::getKey() method does not need …

…to be public.

src/Service/CoolJwt.php

@@ -44,7 +44,7 @@ public function __construct(
      * @return string
      *   The key value.
      */
-    public function getKey() {
+    protected function getKey() {
         $default_config = $this->configFactory->get('collabora_online.settings');
         $key_id = $default_config->get('cool')['key_id'];