HTTP_PROXY support about base HOT 3 OPEN

To properly test proxy, we need a container running without any direct internet access.

This seems relevant: https://forums.docker.com/t/internal-network-between-containers-without-external-network-access/41751/9

Found via https://stackoverflow.com/questions/39913757/restrict-internet-access-docker-container

In theory there could be different proxies during build and during deployment so need to think how that would work. Our ideal is that it simply needs HTTP_PROXY passed in, e.g.

Build: docker build --build-arg HTTP_PROXY=http://10.0.0.1 . -t my_image

Run: docker up -d -e HTTP_PROXY=https://proxy.company.com my_image

We can address it this way:

• For tools (build or runtime) which respect HTTP_PROXY then we do nothing additional
• For tools which can use a proxy but need it provided a different way (e.g. config file, or CLI arg) then we perhaps need to wrap their CLI command to prepare the proxy config before calling the actual command
• For tools which don't support proxy, we need to find alternatives or document that it's impossible. Ideally zero of those in build.

from base.

We probably need to think about DNS too. Maybe the proxy container will also be the DNS forwarder.

from base.

at least apt needs a special handling on install, which we support via APT_HTTP_PROXY env. thats already tested well. also ci tests are using the apt proxy

from base.