"Make a Copy" does not copy attached files

[httpdev]

On alpha.iodide.io revision 1d87c1a, when the user clicks on "Make a Copy", the notebook is cloned, but none of the files attached to it, which may prevent the notebook from working.

What I Did

1. Create a new notebook
2. Go to Files > Add a file, say "test.png"
3. Verify that the file is accessible under /notebooks/<notebook_id>/files/test.png
4. Click on "Make a Copy"
5. With the new notebook, check if the file is accessible unter /notebooks/<Copy_of_notebook_id>/files/test.png

What I Expected

The file should display.

What Happened

500 Internal Server Error message

(if applicable) notebook that reproduces bug

Original notebook: https://alpha.iodide.io/notebooks/4281/files/kaefer.png
Copy: https://alpha.iodide.io/notebooks/4283/files/kaefer.png

[wlach]

Yes this is a known issue, but I don't think we had an issue open for it. Thanks for filing!

[susan-shu-c]

Taking a quick look, seems to be able to add that in here?

Possibly with the help of this or something in /src/shared/utils/file-operations.js