Add enforcementAction to status

[ritazh]

Signed-off-by: Rita Zhang rita.z.zhang@gmail.com

@timothyhinrichs @maxsmythe
Per our discussion for the Dry Run design proposal, this PR updates the status field of Constraint object to include the enforcementAction the violation resulted from.

Example of a Constraint's status field as a result of this PR:

status:
  auditTimestamp: "2019-07-10T06:06:29Z"
  byPod:
  - enforced: true
    id: gatekeeper-controller-manager-0
  violations:
  - enforcementAction: deny
    kind: Pod
    message: 'you must provide labels: {"gatekeeper"}'
    name: nginx-4rfps
    namespace: test
  - enforcementAction: deny
    kind: Pod
    message: 'you must provide labels: {"gatekeeper"}'
    name: nginx-xrxjk
    namespace: test

Once we have implemented the dry run feature, it could be something like:
Constraint for prod

apiVersion: constraints.gatekeeper.sh/v1alpha1
kind: K8sRequiredLabels
metadata:
  name: pod-must-have-gk-prod
spec:
  enforcementAction: dryrun
  match:
    kinds:
      - apiGroups: [""]
        kinds: ["Pod"]
    namespaces:
      - "production"
  parameters:
    labels: ["gatekeeper"]
status:
  auditTimestamp: "2019-07-10T06:06:29Z"
  byPod:
  - enforced: true
    id: gatekeeper-controller-manager-0
  violations:
  - enforcementAction: dryrun
    kind: Pod
    message: 'you must provide labels: {"gatekeeper"}'
    name: nginx-xrxjk
    namespace: production

Constraint for dev

apiVersion: constraints.gatekeeper.sh/v1alpha1
kind: K8sRequiredLabels
metadata:
  name: pod-must-have-gk-dev
spec:
  enforcementAction: deny
  match:
    kinds:
      - apiGroups: [""]
        kinds: ["Pod"]
    namespaces:
      - "dev"
  parameters:
    labels: ["gatekeeper"]
status:
  auditTimestamp: "2019-07-10T06:06:29Z"
  byPod:
  - enforced: true
    id: gatekeeper-controller-manager-0
  violations:
  - enforcementAction: deny
    kind: Pod
    message: 'you must provide labels: {"gatekeeper"}'
    name: nginx-xrxjk
    namespace: dev

[maxsmythe]

LGTM after nits

[timothyhinrichs]

LGTM.

'violations' instead of 'violationsByAction' (like we agreed to the other day) makes sense to me given that the value is an array of objects. It's clean that the enforcementaction is just another field.

[maxsmythe]

LGTM