Pass proxyRegistry credentials to buildImages

[nihussmann]

this feature allows users to set credentials for the registry when the twoRegistries option is enabled.

[schnatterer]

I rebased to main, fixing the conflicts imposed by #221

[schnatterer]

Almost done with your first PR 👏
Please resolve my two findings and then squash all commits into one or two.
My suggestion would be to keep the refactoring commit and squash all further commits (including mine) into one that says something like Add credentials to build images.
You can add the comment about TLS in the extended message, i.e. line 3 or later.

[schnatterer]

@nihussmann Great work!
To not overburden you with complexity in your first ticket, I didn't tell you how to try this new feature in GOP. I tested it and came up with two minor fixes in 9586531.
So I adapted the test to fail and then fixed it 🙂

For testing, I set up harbor as "external" registry, following our manual.

I then pushed the buildImages into harbor:

skopeo copy docker://ghcr.io/cloudogu/gitops-playground --dest-creds Proxy:Proxy12345 --dest-tls-verify=false  docker://localhost:30000/proxy/kubectl
skopeo copy docker://ghcr.io/cloudogu/helm:3.15.4-1 --dest-creds Proxy:Proxy12345 --dest-tls-verify=false  docker://localhost:30000/proxy/helm
 skopeo copy docker://cytopia/yamllint:1.25-0.7 --dest-creds Proxy:Proxy12345 --dest-tls-verify=false  docker://localhost:30000/proxy/yamllint

and finally set up GOP to use the build images:

docker run --rm -t -u $(id -u)  \
   -v ~/.config/k3d/kubeconfig-gitops-playground.yaml:/home/.kube/config  \
    --net=host  \
    gitops-playground:dev \
    --yes --argocd --ingress-nginx --base-url=http://localhost \
    --registry-url=localhost:30000 \
    --registry-path=registry \
    --registry-username=Registry  \
    --registry-password=Registry12345 \
    --registry-proxy-url=localhost:30000 \
    --registry-proxy-username=Proxy \
    --registry-proxy-password=Proxy12345 \
    --petclinic-image=localhost:30000/proxy/eclipse-temurin:11-jre-alpine \
    --kubectl-image=localhost:30000/proxy/kubectl \
    --helm-image=localhost:30000/proxy/helm \
    --yamllint-image=localhost:30000/proxy/yamllint

With this, I can see the two petclinic builds succeed and Jenkins logs tell me that localhost:30000/proxy/ images were used 🥳