Adjust key size in KeyGenerator to 32 bytes.

Changed the key size from 128 bytes to 32 bytes in the KeyGenerator service. This aligns with the expected algorithm requirements and ensures proper cryptographic behavior.

src/Bundle/ChillDocStoreBundle/Service/Cryptography/KeyGenerator.php

@@ -33,7 +33,7 @@ class KeyGenerator
             throw new \LogicException(sprintf("Algorithm '%s' is not supported.", $algo));
         }
 
-        $key = $this->randomizer->getBytes(128);
+        $key = $this->randomizer->getBytes(32);
 
         return [
             'alg' => 'A256CBC',