fix: phpstan level=6

src/Url.php

@@ -3,26 +3,23 @@
 namespace ctiso;
 
 class Url {
-    public $parts = [];
-    /** @var Url */
-    public $parent;
+    /** @var array<string, string> */
+    public array $parts = [];
+    public ?Url $parent;
 
-    function __construct() {
-    }
-
-    function setParent($parent) {
+    function setParent($parent): void {
         $this->parent = $parent;
     }
 
-    function setQuery($parts) {
+    function setQuery($parts): void {
         $this->parts = $parts;
     }
 
-    function addQueryParam($key, $value) {
+    function addQueryParam(string $key, string $value): void {
         $this->parts[$key] = $value;
     }
 
-    function toString() {
+    function toString(): string {
         return '?' . http_build_query(array_merge($this->parts, $this->parent ? $this->parent->parts : []));
     }
 }