feat: post PR comment when migrations are modified

When modified migration files are detected, the script now posts a comment
on the PR to alert reviewers. This makes the warning more visible than just
the workflow annotation. The comment lists all modified migration files and
warns about potential issues for users who have already applied them.

.github/workflows/pipeline.yml

@@ -172,6 +172,9 @@ jobs:
         run: git fetch origin master
 
       - name: Validate migration timestamps
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          PR_NUMBER: ${{ github.event.pull_request.number }}
         run: ./.github/workflows/validate-migrations.sh
 
   check-push-enabled:

.github/workflows/validate-migrations.sh

@@ -57,6 +57,26 @@ if [ -n "$MODIFIED_MIGRATIONS" ]; then
         echo "  - $migration (timestamp: $TIMESTAMP)"
         echo "::warning file=$migration::Modifying existing migration files may cause issues for users who have already applied them"
     done
+
+    # Post a PR review comment if running in GitHub Actions with a PR
+    if [ -n "$GITHUB_TOKEN" ] && [ -n "$GITHUB_REPOSITORY" ] && [ -n "$PR_NUMBER" ]; then
+        COMMENT_BODY="### ⚠️ Modified Migration Files Detected
+
+This PR modifies existing migration files that may have already been applied by users:
+
+$(for m in $MODIFIED_MIGRATIONS; do echo "- \`$m\`"; done)
+
+**Warning:** Modifying migrations that have already been applied can cause issues for existing users. Please ensure this change is intentional and consider the impact on users who have already run these migrations."
+
+        # Use GitHub API to post a PR comment
+        curl -s -X POST \
+            -H "Authorization: token $GITHUB_TOKEN" \
+            -H "Accept: application/vnd.github.v3+json" \
+            "https://api.github.com/repos/$GITHUB_REPOSITORY/issues/$PR_NUMBER/comments" \
+            -d "$(jq -n --arg body "$COMMENT_BODY" '{body: $body}')" > /dev/null
+        
+        echo "Posted PR comment about modified migrations"
+    fi
 fi
 
 if [ "$HAS_ERRORS" = "true" ]; then