Can't configure Mailman Core to expose the REST API externally.

This is being discussed at https://lists.mailman3.org/archives/list/mailman-users@mailman3.org/thread/KPSWRWEUJ5AY2Q6G4OZTR3N4ZRZKNKA6/

The issue is in order to get gunicorn to bind to the non-loopback interface, you need to specify

[webservice]
hostname: 0.0.0.0

However, this means that responses from the REST API will return self_link with a host of 0.0.0.0 which doesn't work for follow up requests.