wip: finalize implementation

src/BusProNet/Model/Insurance.php

@@ -17,7 +17,7 @@ use Symfony\Component\Serializer\Normalizer\DateTimeNormalizer;
 class Insurance
 {
     #[Groups(['api:single', 'api:list'])]
-    public string|int|null $id = null;
+    public string|null $id = null;
 
     #[Groups(['api:single', 'api:list'])]
     public ?string $code = null;
@@ -105,11 +105,6 @@ class Insurance
      */
     public array $individualPrice = [];
 
-    public function __toString(): string
-    {
-        return (string) $this->id;
-    }
-
     /**
      * Returns the subType, with virtual 'PKG' subType for insurance packages.
      *