Add GitLab Runner to CI managed cluster apps

doc/user/clusters/applications.md

@@ -474,6 +474,7 @@ Supported applications:
 - [Ingress](#install-ingress-using-gitlab-ci)
 - [cert-manager](#install-cert-manager-using-gitlab-ci)
 - [Sentry](#install-sentry-using-gitlab-ci)
+- [GitLab Runner](#install-gitlab-runner-using-gitlab-ci)
 
 ### Usage
 
@@ -557,7 +558,7 @@ certManager:
     installed: false
 ```
 
-You can customize the installation of Ingress by defining
+You can customize the installation of cert-manager by defining
 `.gitlab/managed-apps/cert-manager/values.yaml` file in your cluster
 management project. Refer to the
 [chart](https://hub.helm.sh/charts/jetstack/cert-manager) for the
@@ -624,6 +625,37 @@ postgresql:
   postgresqlPassword: example-postgresql-password
 ```
 
+### Install GitLab Runner using GitLab CI
+
+GitLab Runner is installed using GitLab CI by defining configuration in
+`.gitlab/managed-apps/config.yaml`.
+
+The following configuration is required to install GitLab Runner using GitLab CI:
+
+```yaml
+gitlabRunner:
+  installed: true
+```
+
+GitLab Runner is installed into the `gitlab-managed-apps` namespace of your cluster.
+
+In order for GitLab Runner to function, you **must** specify the following:
+
+- `gitlabUrl` - the GitLab server full URL (e.g., `https://example.gitlab.com`) to register the Runner against.
+- `runnerRegistrationToken` - The registration token for adding new Runners to GitLab. This must be
+  [retrieved from your GitLab instance](../../ci/runners/README.md).
+
+These values can be specifed using [CI variables](../../ci/variables/README.md):
+
+- `GITLAB_RUNNER_GITLAB_URL` will be used for `gitlabUrl`.
+- `GITLAB_RUNNER_REGISTRATION_TOKEN` will be used for `runnerRegistrationToken`
+
+You can customize the installation of GitLab Runner by defining
+`.gitlab/managed-apps/gitlab-runner/values.yaml` file in your cluster
+management project. Refer to the
+[chart](https://gitlab.com/gitlab-org/charts/gitlab-runner) for the
+available configuration options.
+
 ## Upgrading applications
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab-foss/merge_requests/24789) in GitLab 11.8.

lib/gitlab/ci/templates/Managed-Cluster-Applications.gitlab-ci.yml

@@ -9,6 +9,7 @@ apply:
     INGRESS_VALUES_FILE: $CI_PROJECT_DIR/.gitlab/managed-apps/ingress/values.yaml
     CERT_MANAGER_VALUES_FILE: $CI_PROJECT_DIR/.gitlab/managed-apps/cert-manager/values.yaml
     SENTRY_VALUES_FILE: $CI_PROJECT_DIR/.gitlab/managed-apps/sentry/values.yaml
+    GITLAB_RUNNER_VALUES_FILE: $CI_PROJECT_DIR/.gitlab/managed-apps/gitlab-runner/values.yaml
   script:
     - gitlab-managed-apps /usr/local/share/gitlab-managed-apps/helmfile.yaml
   only: