Scrape the reviews on an Amazon product page

Returns the review data an Amazon product page shows to a signed-out visitor, as JSON: the overall rating, total reviewCount (global ratings), the 5..1-star histogram (percent per star), the AI customersSay summary (overall text plus per-aspect sentiment, mentions, positive, negative, summary and the quoted review excerpts Amazon shows for the aspect) and the top reviews (each with id, url, author, rating, title, body, date, country, fromOtherCountry, verified, helpfulVotes, variant and images). Identify the product with asin (plus marketplace) or a product url.

Scope: Amazon only shows its full review list to signed-in customers, so this endpoint returns the public slice on the product page - typically 5 to 13 top reviews, local ones first and then reviews from other countries - not a complete review export. When Amazon hides the top reviews behind a sign-in prompt (common on amazon.com), reviewsGated is true and reviews is empty; the rating, histogram and customers-say data, including its review excerpts, are still returned. Every field is always present and is null when the page does not show it. proxy_country defaults to the marketplace's home country; the proxy that served the request is reported as exitCountry (its country) and exitProvider (its type: isp, residential or datacenter).