Recover from failed data uploads #55
Description
We currently do a single request to the server with the experiment data. If this request fails, there's no way to recover from that failure.
We should:
- Try several times in case of failure
- Inform the participant if all retries fail, so that they can try later (with a button/link)
- Maybe save the data in localStorage so that it can be recovered if the page refreshes
It would make sense to move the API class out of the session code and reuse it for both session-based uploads and regular ones. Then the retry functionality could be shared between both options.