* feat(labrinth): support STMP servers with no auth credentials
* feat: set up Mailpit SMTP server as part of our Docker Compose services swarm
* chore(docker-compose): fix healthcheck for mail service
* feat(docker-compose): enable SpamAssassin integration through Postmark
Unlike spinning up yet another container, this requires no
configuration, and is good and simple enough for a funny little feature
developers may occassionally use with non-confidential messages.