add typehints and return types

src/Provider/Node/RandomNodeProvider.php

@@ -31,7 +31,7 @@ class RandomNodeProvider implements NodeProviderInterface
      * @return string System node ID as a hexadecimal string
      * @throws Exception if it was not possible to gather sufficient entropy
      */
-    public function getNode()
+    public function getNode(): string
     {
         $nodeBytes = random_bytes(6);