docs: Clarify kube-mgmt/Gatekeeper K8s docs

Previously the docs detailing the OPA-k8s integration only distinguished
between v1 (kube-mgmt) and v3 (gatekeeper) in the introduction page.
The debugging, primer, and tutorial pages did not explicitly state
which version they were detailing.

This change clarifies that those pages refer to the kube-mgmt
version and provide a pointer to the Gatekeeper readme.

Signed-off-by: Tim Hinrichs <tim@styra.com>

docs/content/kubernetes-debugging.md

@@ -9,6 +9,9 @@ Kubernetes there are a few things you can check to make sure everything is
 configured correctly. If none of these tips work, feel free to join
 [slack.openpolicyagent.org](https://slack.openpolicyagent.org) and ask for help.
 
+The tips below cover the OPA-Kubernetes integration that uses kube-mgmt.
+The [OPA Gatekeeper version](https://github.com/open-policy-agent/gatekeeper) has its own docs.
+
 ### Check for the `openpolicyagent.org/policy-status` annotation on ConfigMaps containing policies
 
 If you are loading policies into OPA via

docs/content/kubernetes-introduction.md

@@ -57,7 +57,7 @@ If you want to kick the tires:
 **Recommendation**: OPA Gatekeeper is currently in beta. If you are getting
 started with admission control, we recommend you try it out.
 
-## How Does It Work With Plain OPA?
+## How Does It Work With Plain OPA and Kube-mgmt?
 
 The Kubernetes API Server is configured to query OPA for admission control
 decisions when objects (e.g., Pods, Services, etc.) are created, updated, or

docs/content/kubernetes-primer.md

@@ -5,7 +5,8 @@ weight: 2
 ---
 
 Read this page if you are new to Kubernetes admission control with OPA and want
-to learn how to write policies for Kubernetes.
+to learn how to write policies for Kubernetes.  It covers the version
+that uses kube-mgmt. The [OPA Gatekeeper version](https://github.com/open-policy-agent/gatekeeper) has its own docs.
 
 ## Writing Policies
 

docs/content/kubernetes-tutorial.md

@@ -5,6 +5,7 @@ weight: 10
 ---
 
 This tutorial shows how to deploy OPA as an admission controller from scratch.
+It covers the OPA-kubernetes version that uses kube-mgmt.  The [OPA Gatekeeper version](https://github.com/open-policy-agent/gatekeeper) has its own docs.
 For the purpose of the tutorial we will deploy two policies that ensure:
 
 - Ingress hostnames must be whitelisted on the Namespace containing the Ingress.