Retrieve all countries

curl --request GET \
  --url https://staging.api.commercengine.io/api/v1/{store_id}/storefront/common/countries \
  --header 'Authorization: Bearer <token>'

{
  "message": "<string>",
  "success": true,
  "content": {
    "countries": [
      {
        "country_name": "<string>",
        "country_code": "<string>",
        "country_iso_code": "<string>",
        "currency_code": "<string>",
        "currency_symbol": "<string>",
        "currency_name": "<string>",
        "flag_icon_url": "<string>"
      }
    ]
  }
}