You are deploying an Apache Airflow directed acyclic graph (DAG) in a Cloud Composer 2 instance. The Cloud Composer instance is located within a subnetwork that has no Internet access. Your workflow involves processing incoming files stored in a Cloud Storage bucket, handling them one file at a time. Rather than executing the DAG at regular intervals according to a schedule, you need the DAG to be triggered reactively, so it runs automatically whenever a new file is uploaded to the Cloud Storage bucket. What approach should you take to implement this functionality?