Initial commit

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

common/db/helper.go

@@ -0,0 +1,7 @@
+package db
+
+import "go.mongodb.org/mongo-driver/mongo"
+
+func IsMongoDupKey(err error) bool {
+	return mongo.IsDuplicateKeyError(err)
+}