Fixed issue where assigning customer group to a category caused an error when trying to duplicate menu

[Riyaprajapat]

Issue Description:

When customer groups are assigned to a category in a Menu, attempting to duplicate that menu results an error. As a result, the menu cannot be duplicated successfully.

Screenshot-1:

Screenshot-2:

Screenshot-3:

Steps to Reproduce:

1. Take a clean shop.
2. Install snowdog/module-menu in the shop.
3. Go to Stores → Configuration → SNOWDOG → Menu → General and set Customer Groups Enabled to Yes. (See Screenshot-1)
4. Create menu, assign customer groups to a category, and save the menu. (See Screenshot-2)
5. Duplicate that menu and observe result( See Screenshot-3).

Expected Results:

The menu should duplicate successfully, even if customer groups are assigned to categories.

Actual Results:

An error occurs during the duplication process, and the menu cannot be duplicated.

Additional Information:

File path: snowdog/module-menu/Service/Menu/Cloner.php

When cloning the menu, the code at line 119 uses $nodeClone->setData($node->getData()); to copy all data. However, in the original menu, the customer_groups field is saved as a JSON string like ["0", "1", "2", "3"], but after cloning, it becomes a plain array or comma-separated values like 0,1,2,3. This difference in format causes the error “Unable to unserialize value. Error: Syntax error” when saving the cloned menu. To fix this, the customer_groups value should be converted back to a JSON string before saving the cloned node.

[adamwaclawczyk]

In code where customerGroups is serialized, unserialized we are using Magento\Framework\Serialize\SerializerInterface

Let's keep this uniform across this module