Create/Update a product

Create a new ecommerce product or update an existing one, identified by the mandatory `id` field. When `updateEnabled` is `false` (the default), the endpoint inserts a new product and returns `201`; if the product ID already exists, a `400` error is returned. When `updateEnabled` is `true`, the endpoint performs an upsert, returning `201` for a new product or `204` for an update. The `name` field is mandatory for creation but optional for updates. Product images are downloaded, validated (max 5 MB, formats: jpeg, jpg, png, bmp, gif, webp), and re-hosted on S3. The `metaInfo` object supports up to 20 keys with a cumulative size limit of approximately 1000 KB.