void insertUser(const std::string& username, const std::string& password) { // Create string data objects from the input strings mongo::StringData usernameData(username); mongo::StringData passwordData(password); // Insert the user into the MongoDB collection auto result = coll.insertOne( // Use the string data objects in the document bsoncxx::builder::stream::document{} << "username" << usernameData << "password" << passwordData << bsoncxx::builder::stream::finalize ); // ... }In this example, StringData is used to create string data objects from the input strings `username` and `password`. These objects are then passed directly to the `insertOne` function, which uses them to construct a `bsoncxx` document. StringData is a part of the MongoDB C++ driver library.