Allow traefik to use ACME http challenge for letsencrypt certificates

[dparv]

Enhancement Proposal

Traefik does support this option https://doc.traefik.io/traefik/https/acme/ so it ideally the charm should implement this so that traefik can request a tls certificate configured in a FQDN config option, serve the tokens under .well-known/acme-challenge/<TOKEN> and acquire the certificate and assign to the service while enabling TLS.