cs: Switch to a stricter way of coding - this might break in a lot of places.

src/Bundle/ChillPersonBundle/Serializer/Normalizer/AccompanyingPeriodOriginNormalizer.php

@@ -7,6 +7,15 @@
  * the LICENSE file that was distributed with this source code.
  */
 
+declare(strict_types=1);
+
+/**
+ * Chill is a software for social workers.
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ */
+
 namespace Chill\PersonBundle\Serializer\Normalizer;
 
 use Chill\PersonBundle\Entity\AccompanyingPeriod\Origin;
@@ -15,7 +24,7 @@ use Symfony\Component\Serializer\Normalizer\NormalizerInterface;
 /**
  * @internal we keep this normalizer, because the property 'text' may be replace by a rendering in the future
  */
-class AccompanyingPeriodOriginNormalizer implements NormalizerInterface
+final class AccompanyingPeriodOriginNormalizer implements NormalizerInterface
 {
     public function normalize($origin, ?string $format = null, array $context = [])
     {