Federation: Add task for setting up placement policies (#4075)

* Add task for setting up placement policies

* Update version of management sidecar in policy engine deployment

* Address @nikhiljindal's comments

- Lower case filenames
- Comments in policy
- Typo fixes
- Removed type LoadBalancer from OPA Service

* Add example that sets cluster selector

Per-@nikhiljindal's suggestion

* Fix wording and templating per @chenopis

docs/tasks/federation/scheduling-policy-admission.yaml

@@ -0,0 +1,29 @@
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: admission
+  namespace: federation-system
+data:
+  config.yml: |
+    apiVersion: apiserver.k8s.io/v1alpha1
+    kind: AdmissionConfiguration
+    plugins:
+    - name: SchedulingPolicy
+      path: /etc/kubernetes/admission/scheduling-policy-config.yml
+  scheduling-policy-config.yml: |
+    kubeconfig: /etc/kubernetes/admission/opa-kubeconfig
+  opa-kubeconfig: |
+    clusters:
+      - name: opa-api
+        cluster:
+          server: http://opa.federation-system.svc.cluster.local:8181/v0/data/kubernetes/placement
+    users:
+      - name: scheduling-policy
+        user:
+          token: deadbeefsecret
+    contexts:
+      - name: default
+        context:
+          cluster: opa-api
+          user: scheduling-policy
+    current-context: default