trigger a google apps script when a file is uploaded to Google Drive

According to https://stackoverflow.com/questions/38242684/can-i-trigger-a-google-script-when-a-file-is-saved-to-google-drive we can either write a time-based trigger to repeatedly poll the drive folder, or use the Push API - https://developers.google.com/drive/api/guides/push (which is much more complicated :) There are also paid services which implement something similar, like https://docs.workato.com/connectors/google-drive/trigger-new-file.html