Authentication for WebDAV server and MQTT broker

[hafklin]

As of now, there is no authentication in place for the WebDAV server to which test results are automatically uploaded and for the MQTT broker. Obviously, this makes the setup unfit for a production deployment.

For the WebDAV server, authentication can be implemented fairly cleanly using OIDC authentication at Traefik. This would require thinking through how trust boundaries should be placed between, e.g., different clusters.

For authentication to the MQTT broker, this likely cannot be solved as cleanly, as OIDC is not really meant to be used with MQTT. A possible solution here would be to place the broker in the peer VPN.