MAPG-199 fix issues found by PHPStan

src/OAuth/GoogleOAuth.php

@@ -4,9 +4,9 @@ use MapGuesser\Interfaces\Http\IRequest;
 
 class GoogleOAuth
 {
-    private static $dialogUrlBase = 'https://accounts.google.com/o/oauth2/v2/auth';
+    private static string $dialogUrlBase = 'https://accounts.google.com/o/oauth2/v2/auth';
 
-    private static $tokenUrlBase = 'https://oauth2.googleapis.com/token';
+    private static string $tokenUrlBase = 'https://oauth2.googleapis.com/token';
 
     private IRequest $request;
 
@@ -36,7 +36,7 @@ class GoogleOAuth
         return self::$dialogUrlBase . '?' . http_build_query($oauthParams);
     }
 
-    public function getToken(string $code, string $redirectUrl)
+    public function getToken(string $code, string $redirectUrl): array
     {
         $tokenParams = [
             'code' => $code,