v0.19.4

Two cartridges fixed after a review of their DESIGN papers, each measured
on a running project.

Fixed

• health_probe v0.3.0: the probes answer in production. Since
  Phoenix 1.8.2, phx.new turns force_ssl on in prod.exs, and
  Plug.SSL runs before any plug of the endpoint, so a probe in plain
  HTTP on the pod's address got a 301. The installer now lists both
  probe routes in force_ssl's exclude: [paths: …] (Plug 1.19). It
  also bounds the readiness check at 500 ms as a whole: the query's own
  timeout does not cover DBConnection's queue, and with the database
  down /ready used to take about 4 s to fail. It now answers 503
  in 0.5 s.
• clustering v0.3.0: the default DNS query names a Service that can
  exist. It was <app>.default.svc.cluster.local with the app name as
  is. A Kubernetes Service name can't have underscores, and nothing said
  the Service had to be headless. Either way the release boots and never
  finds a peer, with nothing in the log. The default is
  <app>-headless now, short so that it resolves in the pod's own
  namespace, and .env carries a note for Kubernetes, Fly.io and
  Compose.
• clustering v0.2.2 and v0.3.1 correct the reasons and the setup
  its papers described, and a test now runs the boot script under dash,
  the /bin/sh of the release image.

Updated

• The README's hero shows the console's Cartridges screen, and its
  captures no longer carry the author's path.

Full record: CHANGELOG.md