quickstart: host.docker.internal DNS not available outside of Docker For Mac

[benjsto]

Is your feature request related to a problem? Please describe. Following the docs for getting up and running, I ran into a hurdle wherein some config values defined use the host.docker.internal host to automatically map to the IP of the Docker host. Unfortunately, that value is only defined in Docker For Mac and not more broadly across Docker environments, as described here: https://github.com/docker/for-linux/issues/264

Describe the solution you'd like If possible, it would be nice to have it be as easy to get SSO up and running in a linux environment as on Mac.

Describe alternatives you've considered A fairly trivial workaround of utilizing the extra_hosts field available to docker-compose works for linux:

extra_hosts:
      - "host.docker.internal:10.0.2.2"

But I assume this may then break the dev experience on a Mac.

Additional context Docker version 18.09.0, build 4d60db4 docker-compose version 1.23.1, build b02f1306

[itsnotvalid]

For quickstart, simply use sso-auth:4180 as internal host would work.