Implement usage of the container image promoter process

[chuckha]

/kind feature

Describe the solution you'd like
Releasing container images is a manual process today. It requires someone with access to gcr.io/cluster-api-provider-aws/cluster-api-aws-controller to push a new image after it is built.

The goal is to automate that process for k8s-sanctioned gcr.io repositories. Take a look here https://github.com/kubernetes-sigs/k8s-container-image-promoter to understand the container image promoter process. There may be some more context kubernetes/k8s.io#158.

We release using the releaser tool found in cmd/release directory in this project. It should also push to the staging directory and at some point prow should promote from that staging directory to production.

Anything else you would like to add:
You will have to get added to some google group list, it should be in the documentation linked above.
There are many small pieces to figure out such as, is there a staging gcr.io bucket already in existence for us? what about production? How frequently does the Prow job run? Should we move old releases into the new production bucket?

/assign @chuckha
/priority important-soon

[chuckha]

cc @amy

[chuckha]

/lifecycle active
@amy is working on this

[amy]

Update: The image promotion process detailed here: https://github.com/kubernetes/k8s.io/tree/master/k8s.gcr.io is not live yet.

See: kubernetes/k8s.io#157

[ncdc]

@detiber I'm thinking all that's left to close this out is to update the releasing.md documentation to talk about the image promoter?

[detiber]

@ncdc indeed, I just need to forward port the docs changes back to the master branch :)