PP-11314 add publishing workflow for release commits

.github/workflows/prevent-merge-if-release-open.yml

@@ -0,0 +1,29 @@
+name: Check for unmerged release PR
+
+on:
+  pull_request:
+
+permissions:
+  pull-requests: read
+
+jobs:
+  check_merge:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check for unmerged release
+        id: check_pr
+        uses: actions/github-script@d7906e4ad0b1822421a7e6a35d5ca353c962f410
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          script: |
+            const prs = await github.rest.pulls.list({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              state: 'open'
+            })
+
+            const openRelease = prs.data.find(pr => pr.user.login === 'alphagov-pay-ci-concourse' && pr.state === 'open')
+
+            if (openRelease) {
+              core.setFailed(`There is an unmerged release PR, please merge it before merging this PR. \n Link: ${openRelease.url}`)
+            }

.github/workflows/publish-package.yml

@@ -0,0 +1,34 @@
+name: Publish to registry
+
+on:
+  push:
+    branches:
+      - main
+
+permissions:
+  contents: read
+
+jobs:
+  tests:
+    uses: ./.github/workflows/run-tests.yml
+  publish:
+    needs: tests
+    runs-on: ubuntu-latest
+    if: "contains(github.event.head_commit.message, '[release]')"
+    steps:
+      - name: Checkout
+        uses: actions/checkout@8e5e7e5ab8b370d6c329ec480221332ada57f0ab
+      - name: Setup Node
+        uses: actions/setup-node@64ed1c7eab4cce3362f8c340dee64e5eaeef8f7c
+        with:
+          node-version-file: '.nvmrc'
+          cache: 'npm'
+          cache-dependency-path: 'package-lock.json'
+      - name: Install dependencies
+        run: npm ci
+      - name: Build project
+        run: npm run build
+      - name: Publish package
+        run: npm publish
+        env:
+          NODE_AUTH_TOKEN: ${{ secrets.NPM_ACCESS_TOKEN }}

.github/workflows/run-tests.yml

@@ -1,10 +1,8 @@
-name: Run Tests
+name: Run tests
 
 on:
   pull_request:
-  push:
-    branches:
-      - main
+  workflow_call:
 
 permissions:
   contents: read

README.md

@@ -113,6 +113,16 @@ For more examples of how metrics can be registered and used, see the [demo code]
 
 `npm run demo` starts the ecs metadata stub and the demo express app 
 
+## Releasing
+
+After a pull request is merged, Concourse will automatically create a new release pull request that increments the package version. 
+
+This pull request must be reviewed and merged by a developer. 
+
+Once the release pull request is merged, GitHub Actions will publish the new versioned package to NPM.
+
+__IMPORTANT__: Other pull requests will be blocked from merging until the release pull request is merged or closed.
+
 ## Licence
 
 [MIT License](LICENSE)