TLS cert for thirdlevel domains

Hi everybody,

we are using traefik (docker-compose version) in our company to route to our internal devops applications and provide tls certificates for those. Right now we are setting up a webserver to deploy demo-versions of our webapplications for our customers. the goal is that we can add multiple webapps into an apache installation and have a single traefik-route pointing to that apache server, so that we dont need to have a new route for every deployment.
I wrote a corresponding traefik route as follows:

      backend = "backend1"
      passHostHeader = true
          rule = ", {subdomain:[a-z]+}"

This works as far that the routing works perfectly, eg. leads to the right webapp on our apache server. Unfortunately the TLS cert for that thirdlevel domain is not generated, as only the traefik default cert is provided to the client.
Is there any way to get the correct certs?