Certificate management
see https://stalw.art/docs/server/reverse-proxy/caddy#certificate-management
cat podman/caddy/caddy/certificates/acme-v02.api.letsencrypt.org-directory/mail.lua.one/mail.lua.one.crt > podman/stalwart/cert/mail.lua.one.pem
cat podman/caddy/caddy/certificates/acme-v02.api.letsencrypt.org-directory/mail.lua.one/mail.lua.one.key > podman/stalwart/cert/mail.lua.one.priv.pem
PROXY Protocol
see https://caddyserver.com/docs/caddyfile/options#proxy-protocol