Add lint job to test UI links to docs

Add a pipeline job to test UI links to docs,
as links break when docs move, especially anchors
when headings change.

.gitlab/ci/docs.gitlab-ci.yml

@@ -59,6 +59,15 @@ docs lint:
     # Check the internal anchor links
     - bundle exec nanoc check internal_anchors
 
+ui-docs-links lint:
+  extends:
+    - .docs:rules:docs-lint
+    - .static-analysis-base
+  stage: test
+  needs: []
+  script:
+    - bundle exec haml-lint -i DocumentationLinks
+
 graphql-reference-verify:
   extends:
     - .default-retry

.haml-lint.yml

@@ -28,7 +28,7 @@ linters:
     max_consecutive: 2
 
   DocumentationLinks:
-    enabled: false
+    enabled: true
     include:
       - 'app/views/**/*.haml'
       - 'ee/app/views/**/*.haml'

app/views/projects/services/prometheus/_external_alerts.html.haml

@@ -3,6 +3,6 @@
 
 - notify_url = notify_project_prometheus_alerts_url(@project, format: :json)
 - authorization_key = @project.alerting_setting.try(:token)
-- learn_more_url = help_page_path('operations/metrics/index.md', anchor: 'external-prometheus-instances')
+- learn_more_url = help_page_path('operations/metrics/alerts.md', anchor: 'external-prometheus-instances')
 
 #js-settings-prometheus-alerts{ data: { notify_url: notify_url, authorization_key: authorization_key, change_key_url: reset_alerting_token_project_settings_operations_path(@project), learn_more_url: learn_more_url, disabled: true } }