chore: apply review advices

Author: bpolaszek

src/Services/UnixTimestampNormalizer.php

@@ -13,7 +13,7 @@ final class UnixTimestampNormalizer implements NormalizerInterface
      */
     public function normalize(mixed $object, string $format = null, array $context = []): int
     {
-        return (int) $object->format('U');
+        return $object->getTimestamp();
     }
 
     public function supportsNormalization(mixed $data, string $format = null, array $context = []): bool

tests/Unit/SerializationTest.php

@@ -47,12 +47,12 @@ public function testSimpleEntityToSearchableArray(): void
             'id' => 12,
             'title' => 'a simple post',
             'content' => 'some text',
-            'publishedAt' => (int) $datetime->format('U'),
+            'publishedAt' => $datetime->getTimestamp(),
             'comments' => [
                 [
                     'id' => null,
                     'content' => 'a great comment',
-                    'publishedAt' => (int) $datetime->format('U'),
+                    'publishedAt' => $datetime->getTimestamp(),
                 ],
             ],
         ];