Add docs preview setup guide

Author: reakaleek

docs/docset.yml

@@ -50,6 +50,7 @@ toc:
           - file: automated.md
           - file: tooling.md
           - file: mapping.md
+          - file: how-to-set-up-docs-previews.md
   - folder: configure
     children:
       - file: index.md

docs/migration/guide/how-to-set-up-docs-previews.md

@@ -0,0 +1,112 @@
+# How to set up docs previews
+
+This guide will help you set up docs previews for your GitHub repository.
+
+## GitHub Workflows
+
+The docs preview system consists of three GitHub Workflows:
+- `docs-build.yml`: Build the docs on a PR
+- `docs-deploy.yml`: Deploy the docs to our preview environment
+- `docs-cleanup.yml`: Cleanup the docs after a PR is merged or closed
+
+
+### Build
+
+This workflow is triggered when a PR is opened. The underlying reusable workflow, builds the documentation and uploads it as an artifact.
+If the `path-pattern` intput does not match any changes in the PR, the workflow will skip the build, but still set a green status check.
+This way you only build and deploy the docs when there are changes to the docs and you can still set it as a required status check.
+
+
+::::{dropdown} .github/workflows/docs-build.yml
+:open:
+
+```yaml
+---
+name: docs-build # The naming is important, don't change it
+
+on:
+  pull_request: ~
+
+jobs:
+docs-preview:
+  uses: elastic/docs-builder/.github/workflows/preview-build.yml
+  with:
+    path-pattern: docs/** # The path to your docs folder.
+  permissions: # Only needs read permissions.
+    contents: read
+    pull-requests: read
+```
+
+::::
+
+### Deploy
+
+This workflow is triggered when the `docs-build` workflow is completed. The underlying reusable workflow, downloads the artifact and deploys the docs to our preview environment.
+
+
+::::{dropdown} .github/workflows/docs-deploy.yml
+:open:
+
+```yaml
+---
+name: docs-deploy
+
+on:
+  workflow_run:
+    workflows: [docs-build] # The name of the docs-build workflow.
+    types:
+      - completed
+
+jobs:
+  docs-preview:
+    uses: elastic/docs-builder/.github/workflows/preview-deploy.yml
+    permissions:
+      contents: none # No need to read the code.
+      id-token: write
+      deployments: write
+      actions: read
+```
+
+::::
+
+### Cleanup
+
+This workflow is triggered when a PR is either merged or closed. The underlying reusable workflow, deletes the docs from the preview environment.
+
+::::{dropdown} .github/workflows/docs-cleanup.yml
+:open:
+
+```yaml
+---
+name: docs-cleanup
+
+on:
+  pull_request_target: # We are using the pull_request_target event, but the code is never checked out.
+    types:
+      - closed
+
+jobs:
+  docs-preview:
+    uses: elastic/docs-builder/.github/workflows/preview-cleanup.yml
+    permissions:
+      contents: none # We don't even grant read permissions, because the code is never checked out.
+      id-token: write
+      deployments: write
+```
+
+::::
+
+## Required Status Checks
+
+To ensure that the docs are always in a deployable state, we need to set up required status checks.
+
+In this case only the `docs-build` workflow is required, which will produce a status check named `docs-preview / build`.
+
+![docs-preview required status check](img/docs-preview-required-status-check.png)
+
+
+## Deployments
+
+If the `docs-build` workflow is successful, the `docs-deploy` workflow will create a deployment visible in the GitHub UI on your PR.
+
+![docs-preview deployment](img/docs-preview-deployment.png)