BUG: unable to upload a large amount of files through the UI

[stchris]

Describe the bug
Uploading a large amount of files through the UI can make an Aleph installation freeze and stop processing.

To Reproduce
Steps to reproduce the behavior:

1. Go to an investigation
2. Click on 'Upload documents'
3. Select a large amount of files (thousands)
4. Aleph will choke and stop processing them.

Expected behavior
Aleph is either able to show and enforce a limit to the number of files being uploaded or it is able to queue the files so that they are processed correctly.

Aleph version
3.15.1

Screenshots

Additional context
The current workaround is to use alephclient

[andresmrm]

Thanks for helping us with this issue, Chris!
Extra context can be found in #3383 .
"Uploading a folder with 8K files worked, but not another with 300K files"

[Rosencrantz]

Options here:

1. Document a limit (1,000 - 5,000?) files max, possibly size could have an impact.
2. Try to fix the UI to handle larger file sets (harder, more time consuming).
3. Limit uploads to single files at a time

[andresmrm]

If 2 is too complex for now, I would prefer 1. Including a warning in the upload dialog about this limitation and a link to crawldir doc or tutorial as an alternative.