🌱 csctl accepts "--node-image-registry" now

[guettli]

csctl accepts "--node-image-registry" now and passes it to the plugin.

Example:

❯ make build; ./csctl create tests/cluster-stacks/docker/ferrol -m hash   --node-image-registry oci://ghcr.io/foo/bar/node-images/staging/
go build -ldflags "-X github.com/SovereignCloudStack/csctl/pkg/cmd.Version=v0.0.2-10-gbf1f8f0-dirty -X github.com/SovereignCloudStack/csctl/pkg/cmd.Commit=bf1f8f0a292e7dcf1a41c0c9b4dccd37ec5c4a09" -o csctl main.go
go build -o csctl-docker csctldocker/csctldocker_main.go
Creating output in releases/docker-ferrol-1-27-v0-sha-bf1f8f0
Calling Provider Plugin: /home/guettli/syself/csctl/csctl-docker
clusterStackPath: tests/cluster-stacks/docker/ferrol
releaseDir: releases/docker-ferrol-1-27-v0-sha-bf1f8f0
nodeImageRegistry: oci://ghcr.io/foo/bar/node-images/staging/     <=== output of plugin
..... pretending to read config: dummyValue
..... pretending to do heavy work (creating node images) ...
Created releases/docker-ferrol-1-27-v0-sha-bf1f8f0

What this PR does / why we need it:

For building node images the plugin needs to know the oci-registry.

The patch makes csctl accept the --node-image-registry flag. It gets passed to the plugin, too.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #100

Special notes for your reviewer:

Please confirm that if this PR changes any image versions, then that's the sole change this PR makes.

TODOs:

• squash commits
• include documentation
• add unit tests

[michal-gubricky]

I tested it with the docker example plugin and it works. I also plan to use this feature in openstack plugin to give the creator of the cluster-stacks option to provide path to registry.yaml where will be stored credentials to the S3 bucket to be able to push built image to S3.