Make PRIVATE_PORT optional for `docker compose port`

[crazybolillo]

Description

"Normal" docker already does this. See the usage for docker port:

$ docker port --help

Usage: docker port CONTAINER [PRIVATE_PORT[/PROTO]]

However docker compose differs:

$ docker compose port --help

Usage:  docker compose port [OPTIONS] SERVICE PRIVATE_PORT

I can look into making a PR if you agree this should be optional.

[torchiaf]

Thanks @artm . Could you provide a screenshot of the rancher-monitoring dashboard ?