[INFRA] Building GitHub Action to comment on community PRs (#7100)

.github/workflows/community_contribution.yml

@@ -0,0 +1,48 @@
+name: "Community contribution"
+on:
+  pull_request_target:
+    types: [opened, reopened]
+
+jobs:
+  community-pr-message:
+    env:
+      USER_LOGIN: ${{ github.event.pull_request.user.login }}
+      IS_ORG_MEMBER: "" # https://github.com/github/vscode-github-actions/issues/47
+    runs-on: ubuntu-latest
+    # https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#permissions
+    permissions:
+      issues: write
+      pull-requests: read
+    steps:
+      - name: "Check for org membership"
+        # https://docs.github.com/en/rest/orgs/members?apiVersion=2022-11-28#check-organization-membership-for-a-user
+        # https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions#example-of-writing-an-environment-variable-to-github_env
+        run: |
+          DATA=$(
+            curl -L -i -w "%{http_code}" \
+            -H "Accept: application/vnd.github+json" \
+            -H "Authorization: Bearer ${{ secrets.EUI_COMMUNITY_PR }}" \
+            -H "X-GitHub-Api-Version: 2022-11-28" \
+            https://api.github.com/orgs/elastic/members/"$USER_LOGIN"
+          )
+
+          HTTP_CODE=$(echo "$DATA" | awk '/([0-9]{3})$/{print}')
+          echo "IS_ORG_MEMBER=$HTTP_CODE" >> "$GITHUB_ENV"
+      - name: "Add comment to community pull requests"
+        uses: actions/github-script@v6
+        if: ${{ env.IS_ORG_MEMBER != '204' }}
+        with:
+          script: |
+            github.rest.issues.createComment({
+              issue_number: context.issue.number,
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              body: "👋 Since this is a community submitted pull request, a Buildkite build has not been started automatically. Would an Elastic organization member please verify the contents of this pull request and kick off a build manually?",
+            });
+
+            github.rest.issues.addLabels({
+              issue_number: context.issue.number,
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              labels: ['community contribution']
+            });