Expose supporting containers internally, not publicly

[tkfu]

Just a minor thing, but there's no particular reason to publicly expose the supporting container ports (which is what the ports directive does). expose only exposes the ports to other containers in the same docker network.

[ggrossetie]

Indeed, since the API of the companion containers is not documented it makes little sense to map the port to the host.

Thanks for the heads up Jon 👍