feature: Support additional ServiceAccounts beyond the default account in each namespace

[developer-guy]

Description

Support additional ServiceAccounts beyond the default account in each namespace

Checklist:

• Fixes issue: #
• I waited for approval before creating this PR

How Has This Been Tested?

$ eval $(minikube docker-env)
$ make docker-build
$ make install deploy
$ arkade install ingress-nginx
$ arkade install cert-manager

$ kubectl create secret docker-registry registry-creds-secret \
  --namespace kube-system \
  --docker-username=$USERNAME \
  --docker-password=$PW \
  --docker-email=$EMAIL

$ kubectl create serviceaccount demo-sa 

$  echo -n "apiVersion: ops.alexellis.io/v1
kind: ClusterPullSecret
metadata:
  name: dockerhub
spec:
  secretRef:
    name: registry-creds-secret
    namespace: kube-system" | k apply -f -

$ kubectl get serviceaccounts default -oyaml 
$ kubectl get serviceaccounts demo-sa -oyaml

Checklist:

I have:

• updated the documentation and/or roadmap (if required)
• read the CONTRIBUTION guide
• signed-off my commits with git commit -s
• added unit tests

[alexellis]

My mistake. This should be controller everywhere. Can you update it?

[developer-guy]

Of course, done.

[alexellis]

Good catch

[developer-guy]

Thank you.

[alexellis]

@developer-guy please can you detail the testing that you did?

I saw that the "How has this been tested" section was removed from the PR template.

[alexellis]

Please add missing fields from https://raw.githubusercontent.com/alexellis/registry-creds/master/.github/pull_request_template.md