Explanation here:
https://github.com/qdm12/gluetun-wiki/blob/main/setup/advanced/vpn-port-forwarding.md
Whenever we receive a new forwarded port (around once a month?) we pass
it to qbit through its API. May require the setting no auth for local
connections in qbit.
Allows to remove the complete port-manager docker container which did
not work very well.