According to this
video on the Google Open Online Education Youtube channel (which is a bit outdated) you will need to use the App Engine project id (or app id) to deploy content using the Course Builder. The App Engine app id has this format: "<app_id>.
appspot.com".
According to the video, you would only need to use the “<app_id>” part.
I recommend you check this
document which will help you deploy an App Engine project to get the project id. Note that Google App Engine charges may apply but it comes with a
free tier.
Note that this Google group is intended for discussions related to Google Cloud Platform App Engine only. If you would like to discuss about Course Builder, I recommend you post a new topic on this
Course Builder Forum.