Updated vendored cluster management project tpl

- The new template includes cert manager 1.4
- Updates documentation about the new version

Changelog: added

doc/user/clusters/migrating_from_gma_to_project_template.md

@@ -90,6 +90,16 @@ some recorded videos with [live examples](#live-examples).
       used in Helm v3. So, the only way to integrate it with this Cluster Management Project is to actually uninstall this app and accept the
       chart version proposed in `applications/vault/values.yaml`.
 
+    - Cert-manager:
+      - For users on Kubernetes version 1.20 or above, the deprecated cert-manager v0.10 is no longer valid and
+        and the upgrade includes a breaking change. So we suggest that you [backup and uninstall cert-manager v0.10](#backup-and-uninstall-cert-manager-v010)
+        , and install cert-manager v1.4 instead. To install this version, uncomment the `applications/cert-manager-1-4/helmfile.yaml`
+        from the [`./helmfile.yaml`](management_project_template.md#the-main-helmfileyml-file).
+        This triggers a pipeline to install the new version.
+      - For users on Kubernetes versions lower than 1.20, you can stick to v0.10 by uncommenting
+        `applications/cert-manager/helmfile.yaml`
+        in your project's main Helmfile ([`./helmfile.yaml`](management_project_template.md#the-main-helmfileyml-file)).
+
 1. After following all the previous steps, [run a pipeline manually](../../ci/pipelines/index.md#run-a-pipeline-manually)
    and watch the `apply` job logs to see if any of your applications were successfully detected, installed, and whether they got any
    unexpected updates.
@@ -104,6 +114,17 @@ some recorded videos with [live examples](#live-examples).
 After getting a successful pipeline, repeat these steps for any other deployed apps
 you want to manage with the Cluster Management Project.
 
+## Backup and uninstall cert-manager v0.10
+
+1. Follow the [official docs](https://docs.cert-manager.io/en/release-0.10/tasks/backup-restore-crds.html) on how to
+  backup your cert-manager v0.10 data.
+1. Uninstall cert-manager by editing the setting all the occurrences of `installed: true` to `installed: false` in the
+   `applications/cert-manager/helmfile.yaml` file.
+1. Search for any left-over resources by executing the following command `kubectl get Issuers,ClusterIssuers,Certificates,CertificateRequests,Orders,Challenges,Secrets,ConfigMaps -n gitlab-managed-apps | grep certmanager`.
+1. For each of the resources found in the previous step, delete them with `kubectl delete -n gitlab-managed-apps {ResourceType} {ResourceName}`.
+   For example, if you found a resource of type `ConfigMap` named `cert-manager-controller`, delete it by executing:
+   `kubectl delete configmap -n gitlab-managed-apps cert-manager-controller`.
+
 ## Live examples
 
 - [Migrating from scratch using a brand new cluster management project](https://youtu.be/jCUFGWT0jS0). Also covers Helm v2 apps migration.

doc/user/infrastructure/clusters/manage/management_project_applications/certmanager.md

@@ -6,16 +6,21 @@ info: To determine the technical writer assigned to the Stage/Group associated w
 
 # Install cert-manager with a cluster management project
 
-> [Introduced](https://gitlab.com/gitlab-org/project-templates/cluster-management/-/merge_requests/5) in GitLab 14.0.
+> - [Introduced](https://gitlab.com/gitlab-org/project-templates/cluster-management/-/merge_requests/5) in GitLab 14.0.
+> - Support for cert-manager v1.4 was [introduced](https://gitlab.com/gitlab-org/project-templates/cluster-management/-/merge_requests/69405) in GitLab 14.3.
 
 Assuming you already have a [Cluster management project](../../../../../user/clusters/management_project.md) created from a
 [management project template](../../../../../user/clusters/management_project_template.md), to install cert-manager you should
 uncomment this line from your `helmfile.yaml`:
 
 ```yaml
-  - path: applications/cert-manager/helmfile.yaml
+  - path: applications/cert-manager-1-4/helmfile.yaml
 ```
 
+NOTE:
+We kept the `- path: applications/cert-manager/helmfile.yaml` with cert-manager v0.10 to facilitate
+the [migration from GitLab Managed Apps to a cluster management project](../../../../clusters/migrating_from_gma_to_project_template.md).
+
 cert-manager:
 
 - Is installed by default into the `gitlab-managed-apps` namespace of your cluster.
@@ -24,7 +29,7 @@ cert-manager:
   email address to be specified. The email address is used by Let's Encrypt to
   contact you about expiring certificates and issues related to your account.
 
-The following configuration in your `applications/cert-manager/helmfile.yaml` is required to install cert-manager:
+To install cert-manager in your cluster, configure your `applications/cert-manager-1-4/helmfile.yaml` to:
 
 ```yaml
 certManager:

doc/user/project/clusters/index.md

@@ -44,6 +44,7 @@ version. The range of supported versions is based on the evaluation of:
 GitLab supports the following Kubernetes versions, and you can upgrade your
 Kubernetes version to any supported version at any time:
 
+- 1.20 (support ends on April 22, 2022)
 - 1.19 (support ends on February 22, 2022)
 - 1.18 (support ends on November 22, 2021)
 - 1.17 (support ends on September 22, 2021)