Add docs for GKE integration

doc/user/permissions.md

@@ -74,6 +74,7 @@ The following table depicts the various user permission levels in a project.
 | Force push to protected branches [^4] |         |            |             |          |        |
 | Remove protected branches [^4]        |         |            |             |          |        |
 | Remove pages                          |         |            |             |          | ✓      |
+| Manage clusters                       |         |            |             | ✓        | ✓      |
 ## Project features permissions

doc/user/project/clusters/index.md

+# Connecting GitLab with GKE
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab-ce/issues/35954) in 10.1.
+
+CAUTION: **Warning:**
+The Cluster integration is currently in **Beta**.
+
+Connect your project to Google Container Engine (GKE) in a few steps
+without the need to provide any credentials for your Kubernetes cluster.
+
+With a cluster associated to your project, you can use Review Apps, deploy your
+applications, run your pipelines, and much more in an easy way.
+
+NOTE: **Note:**
+The Cluster integration will eventually supersede the
+[Kubernetes integration](../integrations/kubernetes.md). For the moment,
+you can create only one cluster.
+
+## Prerequisites
+
+In order to be able to manage your GKE cluster through GitLab, the following
+prerequisites must be met:
+
+- The [Google authentication integration](../../../integration/google.md) must
+  be enabled in GitLab at the instance level. If that's not the case, ask your
+  administrator to enable it.
+- Your Google account must be associated with your GitLab one. If you haven't
+  done this already, you will be asked in the **Cluster** page.
+- Your associated Google account must have the right privileges to manage
+  clusters on GKE.
+- You must have Master [permissions] in order to be able to access the **Cluster**
+  page.
+
+If all of the above requirements are met, you can proceed to add a new cluster.
+
+TIP: **Tip:**
+Check your existing connected accounts by navigating to your account's settings
+under the **Account > Social sign-in** section.
+
+## Adding a cluster
+
+NOTE: **Note:**
+You need Master [permissions] and above to add a cluster.
+
+To add a new cluster:
+
+1. Navigate to your project's **CI/CD > Cluster** page.
+1. Connect your Google account if you haven't done already by clicking the
+   "Sign-in with Google" button.
+1. Fill in the requested values:
+  - **Cluster name** (required) - The name you wish to give the cluster.
+  - **GCP project ID** (required) - The ID of the project you created in your GCP
+    console that will host the Kubernetes cluster. This must **not** be confused
+    with the project name. Learn more about [Google Cloud Platform projects](https://cloud.google.com/resource-manager/docs/creating-managing-projects).
+  - **Zone** - The zone under which the cluster will be created. Read more about
+    [the available zones](https://cloud.google.com/compute/docs/regions-zones/).
+  - **Number of nodes** - The number of nodes you wish the cluster to have.
+  - **Machine type** - The machine type of the Virtual Machine instance that
+    the cluster will be based on. Read more about [the available machine types](https://cloud.google.com/compute/docs/machine-types).
+  - **Project namespace** - The unique namespace for this project. By default you
+    don't have to fill it in; by leaving it blank, GitLab will create one for you.
+1. Click the **Create cluster** button.
+
+After a few moments your cluster should be created. If something goes wrong,
+you will be notified.
+
+Now, you can proceed to [enable the Cluster integration](#enabling-or-disabling-the-cluster-integration).
+
+## Enabling or disabling the Cluster integration
+
+After you have successfully added your cluster information, you can enable the
+Cluster integration:
+
+1. Click the "Enabled/Disabled" switch
+1. Hit **Save** for the changes to take effect
+
+You can now start using your Kubernetes cluster for your deployments.
+
+To disable the Cluster integration, follow the same procedure.
+
+## Removing a cluster
+
+NOTE: **Note:**
+You need Master [permissions] and above to remove a cluster integration.
+
+NOTE: **Note:**
+When you remove a cluster, you only remove its relation to GitLab, not the
+cluster itself. To remove the cluster, you can do so by visiting the GKE
+dashboard or using `kubectl`.
+
+To remove the Cluster integration from your project, simply click on the
+**Remove integration** button. You will then be able to follow the procedure
+and [add a cluster](#adding-a-cluster) again.
+
+[permissions]: ../../permissions.md

doc/user/project/index.md

@@ -63,6 +63,8 @@ common actions on issues or merge requests
      browse, and download job artifacts
      - [Pipeline settings](pipelines/settings.md): Set up Git strategy (choose the default way your repository is fetched from GitLab in a job),
      timeout (defines the maximum amount of time in minutes that a job is able run), custom path for `.gitlab-ci.yml`, test coverage parsing, pipeline's visibility, and much more
+  - [GKE cluster integration](cluster/index.md): Connecting your GitLab project
+    with Google Container Engine
 - [GitLab Pages](pages/index.md): Build, test, and deploy your static
 website with GitLab Pages