origin test server: origin-443

  /echo /echo/raw /health /.well-known/acme-challenge/{token}
  /status/{code} /response-headers?K=V /set-cookie?k=v /redirect?to=&code=
  /size/{bytes} /upload /delay/{sec} /drip?duration=&chunks= /sse /ws
  /close /no-keepalive
  /cache/max-age/{sec} /cache/no-store /cache/etag /cache/last-modified /cache/vary
  /html /json /xml /text /gzip

spec: ORIGIN-SERVER-DESIGN.md