Update documentation and specs

This updates the documentation to reflect the instance
template repository functionality for the metrics
dashboard custom templates

changelogs/unreleased/jivanvl-backend-metrics-dashboard-template.yml

+---
+title: Add custom metrics dashboard templates supports
+merge_request: 37523
+author:
+type: added

doc/operations/metrics/dashboards/develop.md

@@ -10,33 +10,23 @@ GitLab provides a template to make it easier for you to create templates for
 [custom dashboards](index.md). Templates provide helpful guidance and
 commented-out examples you can use.
 
-## Create a new dashboard template
+## Applying dashboard template
 
-To create a new dashboard template to speed the development of more dashboards:
+Navigate to the browser-based editor of your choice:
 
-1. Navigate to the browser-based editor of your choice:
-
-   - *To use the repository view,* navigate to **{doc-text}** **Repository > Files**.
-   - *To use the [Web IDE](../../../user/project/web_ide/index.md),* click
-     **Web IDE** when viewing your repository.
-1. Create a template file that meets your needs, using the [custom dashboard syntax](yaml.md).
-1. Save the template file in the `lib/gitlab/metrics/templates` directory,
-   with a name matching the pattern `*.metrics-dashboard.yml`.
-1. Reload the editor you used to create the new template and ensure the template
-   is now available for use:
-
-   - *In the repository view,* click **{plus}** **Add to tree** and select **New file**,
+### *Repository view* 
+  1. Navigate to **{doc-text}** **Repository > Files**.
+  1. Click **{plus}** **Add to tree** and select **New file**,
              then click **Select a template type** to see a list of available templates:
              ![Metrics dashboard template selection](img/metrics_dashboard_template_selection_v13_3.png)
-   - *In the Web IDE,* click **Web IDE** when viewing your repository, click
-     **{doc-new}** **New file**, then click **Choose a template** to see a list of
-     available templates:
+             
+### *[Web IDE](../../../user/project/web_ide/index.md)* 
+  1. Click **Web IDE** when viewing your repository.
+  1. Click **{doc-new}** **New file**, then click **Choose a template** to see a list of available templates:
   ![Metrics dashboard template selection WebIDE](img/metrics_dashboard_template_selection_web_ide_v13_3.png)
 
-## Template location and naming
+## Custom dashboard template **(PREMIUM ONLY)**
 
-For templates to be valid and available for use, they must:
+To enable and use a custom dashboard templates on your GitLab instance please follow
+[general guide](../../../user/admin_area/settings/instance_template_repository.md) on custom file templates
 
-1. Reside in the `lib/gitlab/metrics/templates` directory.
-1. Be named with the `*.metrics-dashboard.yml` suffix.
-1. Follow the [custom dashboard syntax](yaml.md).

doc/user/admin_area/settings/instance_template_repository.md

@@ -39,6 +39,7 @@ are supported:
 | `.gitignore`            | `gitignore`          | `.gitignore`  |
 | `.gitlab-ci.yml`        | `gitlab-ci`          | `.yml`        |
 | `LICENSE`               | `LICENSE`            | `.txt`        |
+| `metrics-dashboard.yml` | `metrics-dashboards` | `.yml`        |
 
 Each template must go in its respective subdirectory, have the correct
 extension and not be empty. So, the hierarchy should look like this:
@@ -57,6 +58,9 @@ extension and not be empty. So, the hierarchy should look like this:
 |-- LICENSE
     |-- custom_license.txt
     |-- another_license.txt
+|-- LICENSE
+    |-- custom_metrics-dashboard.yml
+    |-- another_metrics-dashboard.yml
 ```
 
 Once this is established, the list of custom templates will be included when

ee/spec/lib/gitlab/template/custom_templates_spec.rb

@@ -36,7 +36,8 @@ RSpec.describe "Custom file template classes" do
     ::Gitlab::Template::CustomDockerfileTemplate,
     ::Gitlab::Template::CustomGitignoreTemplate,
     ::Gitlab::Template::CustomGitlabCiYmlTemplate,
-    ::Gitlab::Template::CustomLicenseTemplate
+    ::Gitlab::Template::CustomLicenseTemplate,
+    ::Gitlab::Template::CustomMetricsDashboardYmlTemplate
   ].each do |template_class|
     describe template_class do
       let(:name) { template_class.name.demodulize }