Automatically resume unfinished uploads after site-reload

[JammingBen]

Currently, we are able to pause and resume uploads. In the future we also want to possibility to resume cancelled/unfinished uploads (e.g. when cancelling an upload directly, or cancelling it via a page reload).

Tus & Uppy already bring the prerequisites for this feature, as each upload will be stored in the local storage. Currently, those entries will be removed on cancel though (might be related to the removeFingerprintOnSuccess option). Hence we need to make sure those entries stay present on cancel so they can be resumed later.

[JammingBen]

I digged into this a bit.

With #8055, it is possible to resume a cancelled upload, even after a site reload. But the user needs to manually upload the file again. Thanks to tus, the upload will then continue were it left off.

For automatically resuming uploads, Uppy provides a plugin called Golden Retriever. I tried it, unfortunately it didn't work out of the box when trying with a folder including ~150 files. It's recommended to use a service worker for this, which I didn't. Maybe that would improve things. Or maybe our custom tus plugin and/or the logic for folder uploads causes issues here.