Build configs for preview builds through GKE

Build configs for preview builds through GKE

## Description ✍️

Moving the docs preview builds from Cloudflare to "websitecloud" Google Cloud Project which is currently handling the staging and production deployments:

The preview triggers are expected to be called only on changes to the docs folder

PR-URL: hasura/graphql-engine-mono#6999
GitOrigin-RevId: 1699fe7677ebc03b8ce6338394e91d8e848640c3

Author: console-log-kai

docs/.dockerignore

@@ -0,0 +1,6 @@
+.DS_Store
+.git
+.gitignore
+node_modules
+yarn-error.log
+.docusaurus

docs/Dockerfile

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+# Used only for preview builds
+
+FROM --platform=linux/amd64 node:17-alpine
+
+ENV release_mode="staging"
+
+ENV BUILD_VERSION="2.0"
+
+RUN apk add --update git \
+    bash \
+    yarn
+
+#WORKDIR /app
+WORKDIR /graphql-engine/docs
+
+# Bundle app source
+COPY . .
+
+RUN yarn
+
+RUN yarn build
+
+CMD ["yarn", "run", "serve", "-p", "8080", "--host", "0.0.0.0"]

docs/preview_cloud_build.yaml

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+steps:
+
+#kaniko
+- name: 'gcr.io/kaniko-project/executor:latest'
+  id: kaniko
+  args:
+      [
+          "--dockerfile=./Dockerfile",
+          "--context=dir:///workspace/docs",
+          "--cache=false",
+          "--cache-ttl=1h",
+          "--destination=us-west1-docker.pkg.dev/${PROJECT_ID}/docusaurus/docusaurus:${_PR_NUMBER}-${SHORT_SHA}",
+      ]
+      
+- id: "deploy revision with tag"
+  name: "gcr.io/google.com/cloudsdktool/cloud-sdk"
+  entrypoint: "gcloud"
+  args:
+     [
+        "run",
+        "deploy",
+        "${_SERVICE_NAME}",
+        "--platform",
+        "managed",
+        "--region",
+        "${_REGION}",
+        "--image",
+        "us-west1-docker.pkg.dev/${PROJECT_ID}/docusaurus/docusaurus:${_PR_NUMBER}-${SHORT_SHA}",
+        "--tag",
+        "pr-${_PR_NUMBER}",
+        "--no-traffic",
+     ]
+
+- id: "link revision on pull request"
+  name: "gcr.io/${PROJECT_ID}/deployment-previews" # our custom builder
+  secretEnv: ["GITHUB_TOKEN"]
+  args:
+     [
+        "set",
+        "--project-id",
+        "${PROJECT_ID}",
+        "--region",
+        "${_REGION}",
+        "--service",
+        "${_SERVICE_NAME}",
+        "--pull-request",
+        "${_PR_NUMBER}",
+        "--repo-name",
+        "${_GITHUB_REPO}",
+        "--commit-sha",
+        "${SHORT_SHA}",
+     ]
+     
+timeout: 3600s
+
+substitutions:
+  _SERVICE_NAME: docusaurus
+  _REGION: us-west2
+  _GITHUB_REPO: $(pull_request.pull_request.head.repo.full_name)
+
+options:
+  dynamicSubstitutions: true
+  workerPool: 'projects/websitecloud-352908/locations/us-west2/workerPools/gke-vpn-pool'
+
+availableSecrets:
+  secretManager:
+    - versionName: projects/$PROJECT_ID/secrets/github_token/versions/latest
+      env: "GITHUB_TOKEN"