[new feature] fully support `signadot local connect` inside Docker

[scott-cotton]

New feature or functionality
What would you like Signadot to do?
running signadot local connect inside docker should work.

Additional considerations
Anything in particular to think about regarding this new feature?

[scott-cotton]

the signadot-cli docker image only contains the cli itself. It does not contain sudo and it does not contain what is necessary to connect locally via portforward for many k8s providers (for example was eks auth support). This is because we did not initially target running signadot local inside of docker as an intended use case. But, you can build an image which contains sudo and base relevant tools:

FROM signadot/signadot-cli as cli
FROM ubuntu
COPY --from=cli /signadot /usr/bin/signadot
RUN apt-get update
RUN apt-get install sudo -y
RUN apt-get install iptables -y
RUN apt-get install ca-certificates -y

and use the ControlPlaneProxy or ProxyAddress connection methods.

The PortForward connection method (the default) is harder to set up, because it often depends on other auth mechanisms which need to be in the image as well, and those mechanisms vary from k8s provider to k8s provider.