Update product variant

curl --request PATCH \
  --url https://api.shoppex.io/dev/v1/products/{id}/variants/{variantId} \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "file_id": null,
  "dynamic_webhook": null
}
'

{
  "data": {
    "id": "variant_1",
    "uniqid": "variant_1",
    "product_uniqid": "prod_1",
    "file_id": null,
    "dynamic_webhook": null,
    "title": "Updated",
    "description": null,
    "price": 15,
    "price_modifier": null,
    "stock": 4,
    "stock_delimiter": null,
    "license_period": null,
    "option_values": null,
    "is_default": false,
    "sort_order": 1,
    "created_at": 1711953600,
    "updated_at": 1711953900
  }
}