Use Alpine base image

[HPPinata]

wgquick (apparently) depends on bash and openresolv.

Without those packages removing an Interface is impossible and causes an error message to appear in the webui:

• No Bash: exec complains about "bash no such file in $PATH"
• No openresolv: resolvconf -f -d interface returns with error 127

Not having a Shell in the container also makes debugging a lot more annoying.

This enables deletion of interfaces in the webui, eases debugging and only adds about 3MB in size.

[HPPinata]

Testing environment was the wgportal/wg-portal:latest docker image running on top of OpenSUSE MicroOS in an x86_64 VM using the official docker and docker-compose packages with cap_add: - NET_ADMIN and network_mode: host set. I even tested privileged: true with no change in observed behaviour.

I tested both removal of imported and new interfaces, behaviour is consistent between both cases (does not work without changes, works after adding bash and openresolv). I also tested whether openresolv needed to be installed in the container, on the host, on both or neither system. Result: installing bash and openresolv just in the container is sufficient
No build errors or other issuses were observed after applying the changes. No other changes were made to the system or install.

The configuration file was quite minimal and based on the config.yml.sample with the auth section removed.
Import existing was changed between true and false (with a full docker system prune -a -f --volumes in between to test removal of preexisting vs. completely new interfaces:

advanced:
  log_level: trace

core:
  admin_user: user@example.net
  admin_password: SecurePassword
  import_existing: false

web:
  external_url: https://my.external.url
  request_logging: true

[h44z]

lgtm =)