This seems possible with the API but is probably more work than most coaches will want to do. I think you could create an external application using oauth with intervals to get this done. The end user would be linked to intervals to login (which may include creating an account), and then once they approved access for the external application that app would have permissions and user id needed to call the share folder api.
External applications require one-off approval from David right now, and this is a chunk of boilerplate work for every coach who wanted to do this same thing, so it’s not a good approach compared to something built-in.
(I also haven’t actually tried this, just seems like a feasible approach from my understanding of the API.)