Add remaining missing return types to safe methods

Author: wouterj

Transport/Dsn.php

@@ -82,7 +82,7 @@ public function getPort(int $default = null): ?int
         return $this->port ?? $default;
     }
 
-    public function getOption(string $key, mixed $default = null)
+    public function getOption(string $key, mixed $default = null): mixed
     {
         return $this->options[$key] ?? $default;
     }