Improve queueing for deletion

[nfebe]

Bug description

See : #45237 (review)

• Update frontend to provide feedback about not closing browser/window when multiple delete.
• Explore means to queue deletion in the backend jobs.

[skjnldsv]

Preventing closing with onbeforeunload is the cleanest way imho

[AndyXheli]

I read a previous comment that once this operation starts a user needs to leave the windows open I think it would be more productive that once a users starts this operation they can leave the page and do other tasks and not wait for this job to complete. The job should be completed in the backend. Currently, that's how Google Drive, Onedrive, etc. You don't need to keep the windows open or two stay on the delete page. Once the delete operation starts, you can leave that page and do other stuff.

[skjnldsv]

Yep, there is currently no asynchronous operations.
That is kind of a different topic

[AndyXheli]

Do you think that would be something that will get implemented?

[skjnldsv]

@AndyXheli at some point I hope so, that would allow to only send one request for a batch of actions.
Then we would not even need to throttle them. But we're using webdav, so we would have to create our own plugin or implementation for this. I think there is an opened issue about this already :)