Include Digest and ImageID in /services response

[foot]

/images is returning Digest and ImageId which comes from the image repository, but we don't have the Digest/ImageId of the pods running in the cluster.

[foot]

It would be great to get CreatedAt too but I'm not sure if that piece of information resides in the same place?

[squaremo]

I looked into this. It's not straight-forward to get this info from kubernetes -- controllers don't keep track of the digest (unless you specify one in the manifest), since they are just a template for the pods.

Individual pods seem to have an image ID of some kind:

$ kubectl get pod -n kube-system =l name=flux -o yaml
apiVersion: v1
items:
- apiVersion: v1
  kind: Pod
  metadata:
# ...
  status:
    conditions:
    - lastProbeTime: null
      lastTransitionTime: 2018-02-07T13:31:34Z
      status: "True"
      type: Initialized
    - lastProbeTime: null
      lastTransitionTime: 2018-02-08T18:24:54Z
      status: "True"
      type: Ready
    - lastProbeTime: null
      lastTransitionTime: 2018-02-07T13:31:34Z
      status: "True"
      type: PodScheduled
    containerStatuses:
    - containerID: docker://7733a0c9ab1f4048e6d1b43c41207a2ea3a6b13211afc91f4311fc661920c960
      image: quay.io/weaveworks/flux:feature-repo-sync-99acb551
      imageID: docker://sha256:a6a480bea993c2d9fa7f6d138a69f1a1525ae252498c03ebbba0818ab3b5be13

.. but there will usually be more than one pod that's attributable to a controller, and they may well have different images running (either because a rollout is in progress, or because for some reason the images at each host differ).

[foot]

Gotcha.

If the new /images summary tells the UI what flux thinks the current image is that would be fine too.

This issue should be described as the problem really: The UI would like to know: currentImage.ID and currentImage.CreatedAt to show that information in https://github.com/weaveworks/service-ui/pull/1907. The solution proposed in #913 will probably solve that so we could close this.