Add GHA to verify commit sign off

Signed-off-by: annecyh <anne.chew@canonical.com>

Author: AnneCYH

.github/workflows/verify-commit-signoff.yml

@@ -0,0 +1,41 @@
+name: Verify Commit Signoff
+
+on:
+  pull_request:
+    branches:
+      - "main" # Run on pull requests to the main branch
+
+jobs:
+  verify-signoff:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Validate commits
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          # Ensure both commits in the range exist locally
+          if [ "${{ github.event.before }}" = "0000000000000000000000000000000000000000" ]; then
+            # First push, check all commits
+            COMMITS=$(git rev-list ${{ github.sha }})
+          else
+            # Fetch the commit range
+            git fetch origin ${{ github.event.before }} --quiet
+            COMMITS=$(git log --format='%H' ${{ github.event.before }}..${{ github.sha }})
+          fi
+          
+          # Check each commit
+          for COMMIT in $COMMITS; do
+            MESSAGE=$(git show -s --format='%B' $COMMIT)
+
+            # Check for sign-off
+            if ! echo "$MESSAGE" | grep -q "Signed-off-by:"; then
+              echo "❌ Commit $COMMIT is missing a 'Signed-off-by:' line."
+              exit 1
+            fi
+          done
+
+          echo "✅ All commits are properly signed off."