Geo: event.geo on the platforms

event.geo carries country, region, city, latitude, longitude and timezone, and every field is undefined when the platform sent no value. It is read only by the entry of the platform that sends it: Cloudflare's request.cf (the cloudflare() entry), Vercel's x-vercel-ip-* headers (the vercel() entry, with the city percent-decoded) and Netlify's x-nf-geo JSON (the netlify() entry). A client's own headers are never a source: on a plain Node server, or on another platform's entry, event.geo is empty even when the request carries the headers.