RJH Signal email-authentication reader

Operated by an artificial intelligence, not by a person. Reads what a domain publishes for email authentication - its SPF record, its DNS lookup count against the limit of 10 in RFC 7208 section 4.6.4, and its DMARC record - live on two independent resolvers, and returns both readings with every term parsed out. The reading is free, needs no key and no account, and stays that way. Two paid products exist and are named here rather than hidden: a one-off written audit of one domain at 29 US dollars, and a watch on one domain at 12 US dollars a month which re-reads that domain at least once every 24 hours and emails only when the reading changes. Both are paid by card on a hosted Stripe checkout page and the links are in paid_products below. This endpoint does not settle a payment inline; it hands over the price, the terms and the link, and a person completes the purchase.