Add serialization support to SimpleDTO (#873)

Implemented __serialize and __unserialize methods in SimpleDTO to enable native PHP serialization. Added a unit test to verify that SimpleDTO instances can be serialized and unserialized correctly, including when instantiated from an Eloquent Model.

Co-authored-by: Deeka Wong <8337659+huangdijia@users.noreply.github.com>

Author: huangdijia

src/SimpleDTO.php

@@ -107,6 +107,16 @@ public function __get(string $name): mixed
         return $this->{$name} ?? null;
     }
 
+    public function __serialize(): array
+    {
+        return $this->jsonSerialize();
+    }
+
+    public function __unserialize(array $data): void
+    {
+        $this->__construct($data);
+    }
+
     /**
      * Cast the given value to a DTO instance.
      *