ci(stale): create `stale.yml` workflow

- Treat issues and PRs separately
- At the end, generate a cross-linked summary with all processed issues/PRs

.github/workflows/stale.yml

@@ -0,0 +1,105 @@
+name: Stale and close inactive issues/PRs
+
+on:
+  schedule:
+    - cron: "30 1 * * *"  # each day at 1:30AM
+  workflow_dispatch:      # or manually
+
+permissions:
+  issues: read
+  pull-requests: read
+
+# This allows a subsequently queued workflow run to interrupt previous runs
+concurrency:
+  group: '${{ github.workflow }} @ ${{ github.head_ref || github.ref || github.run_id }}'
+  cancel-in-progress: true
+
+jobs:
+
+  process-issues:
+    name: Process Issues
+
+    permissions:
+      issues: write
+
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/stale@v5
+        with:
+          operations-per-run: 30
+          days-before-issue-stale: 30
+          days-before-issue-close: 7
+          stale-issue-label: "stale"
+          close-issue-label: "stale: closed"
+          stale-issue-message: "This issue is stale because it has been open for 30 days with no activity."
+          close-issue-message: "This issue was closed because it has been inactive for 7 days since being marked as stale."
+          remove-issue-stale-when-updated: true
+          exempt-issue-labels: "👥 discussion,👀 Needs Review,📌 pinned"
+          days-before-pr-stale: -1
+          days-before-pr-close: -1
+
+  process-prs:
+    name: Process Pull Requests
+
+    permissions:
+      pull-requests: write
+
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/stale@v5
+        with:
+          operations-per-run: 30
+          days-before-pr-stale: 30
+          days-before-pr-close: 7
+          stale-pr-label: "stale"
+          close-pr-label: "stale: closed"
+          stale-pr-message: "This pull request is stale because it has been open for 30 days with no activity."
+          close-pr-message: "This pull request was closed because it has been inactive for 7 days since being marked as stale."
+          remove-pr-stale-when-updated: true
+          exempt-pr-labels: "👥 discussion,👀 Needs Review"
+          exempt-draft-pr: true
+          days-before-issue-stale: -1
+          days-before-issue-close: -1
+
+  generate-summary:
+    name: GitHub report
+
+    needs: [process-issues, process-prs]
+
+    runs-on: ubuntu-latest
+
+    steps:
+      - run: |
+          echo "### Staled issues"  \
+            >> $GITHUB_STEP_SUMMARY
+          echo "$STALED_ISSUES"  \
+            | jq --raw-output 'map("* [#\(.number)](\(env.GITHUB_ISSUES_URL)/\(.number)): \(.title)") | join("\n")'  \
+            >> $GITHUB_STEP_SUMMARY
+
+          echo "### Staled pull requests"  \
+            >> $GITHUB_STEP_SUMMARY
+          echo "$STALED_PRS"  \
+            | jq --raw-output 'map("* [#\(.number)](\(env.GITHUB_PULL_URL)/\(.number)): \(.title)") | join("\n")'  \
+            >> $GITHUB_STEP_SUMMARY
+
+          echo "### Closed issues"  \
+            >> $GITHUB_STEP_SUMMARY
+          echo "$CLOSED_ISSUES"  \
+            | jq --raw-output 'map("* [#\(.number)](\(env.GITHUB_ISSUES_URL)/\(.number)): \(.title)") | join("\n")'  \
+            >> $GITHUB_STEP_SUMMARY
+
+          echo "### Closed pull requests"  \
+            >> $GITHUB_STEP_SUMMARY
+          echo "$CLOSED_PRS"  \
+            | jq --raw-output 'map("* [#\(.number)](\(env.GITHUB_PULL_URL)/\(.number)): \(.title)") | join("\n")'  \
+            >> $GITHUB_STEP_SUMMARY
+        env:
+          GITHUB_REPO_URL:   ${{ format('{0}/{1}', github.server_url, github.repository) }}
+          GITHUB_ISSUES_URL: ${{ format('{0}/{1}/issues', github.server_url, github.repository) }}
+          GITHUB_PULL_URL:   ${{ format('{0}/{1}/pull', github.server_url, github.repository) }}
+          STALED_ISSUES: ${{ needs.process-issues.outputs.staled-issues-prs }}
+          CLOSED_ISSUES: ${{ needs.process-issues.outputs.closed-issues-prs }}
+          STALED_PRS:    ${{ needs.process-prs.outputs.staled-issues-prs }}
+          CLOSED_PRS:    ${{ needs.process-prs.outputs.closed-issues-prs }}