Allow to use a custom Service Account

[LarryGF]

I think a nice addition to the chart would be to allow to skip the default Service Account creation and to specify the name of another one created separately.

My use case is as follows: I am injecting the Google project Id from Argocd to my helm charts, allowing me to reference it inside my Chart's templates without having to explicitly set it in the values.yaml. The issue is that, even if I create a separate Service Account with the correct annotations, it will still create a default Service Account and reference it in the Deployment, RoleBinding and ClusterRoleBinding and from the chart I don't have a way to reference my custom Service Account.

This leaves two options if the Helm Chart doesn't support a custom, separate Service Account:

• Create my custom service account with the same name as the default one, which makes ArgoCD raise a warning about duplicated resources (and I'm not sure how reconciliation will work in the long run)
• Directly apply the manifest with my modifications in place, but this will be tiresome to maintain, since I will have to constantly update the manifest whenever a new version of the helm chart is released.

If this sounds like something more people would want I'd be more than happy to work on a PR

[golgoth31]

Hi, I made the PR #143 to fix this issue but nobody seems to approve it :(