this worked:    std::unordered_map<std::string, common::AttributeValue> attributes_;
    attributes_[std::string("event_type")] = std::string("my event");
    attributes_[std::string("flow_id")] = 4567;
    attributes_[std::string("u32")]  = 123;
    attributes_[std::string("bool")] = true;

    logger->EmitLogRecord(opentelemetry::logs::Severity::kInfo, "Body: User login via gRPC", attributes_);