MongoDB support, concurrent streams, player/backend file handling refactor, and more!

[Tzahi12345]

Prologue

Normally I don't like to combine unrelated additions into one PR but the concurrent streaming functionality (see #171) and refactor of the player component go hand in hand. Once that was done, it seemed natural to update file download (to browser)/deletion process to use file UIDs instead of relying on their name (which we confusingly called ID).

Once I made these changes, I couldn't help myself to refactoring all DB calls to be more platform-agnostic. And thus, MongoDB support was born.

I also added some backend unit tests as a sanity check for DB operations and file access on shared videos -- we didn't have any unit tests and so this is much needed. There's still a lot of backend refactoring to do but this is a huge step forward.

New additions

• MongoDB support!
  • This is optional, and it's easy enough to "transfer" the MongoDB tables into a new local_db.json file where you can modify properties and transfer it back. Or, you can just keep it local and it'll work just as it did before.
  • docker-compose.yml is updated to include MongoDB, not sure if this is the best approach but worst case it can be taken out and allows it to work out of the box
  • Closes DB migration on BIG databases will take several days... #295
  • Closes DB Screwed up for no apparent reason.  #368
• Concurrent streams
  • You can now watch shared videos together with friends at the same time! We're calling it concurrent streams, and it basically matches someone's playback to yours. You do this by clicking "Watch together" under a video and then selecting "Start stream". Your friends can then do the same except they will only see "Join stream", and that's all that's required! See a demo if it working on this comment.
  • Closes Synchronize video/audio playback with multiple concurrent users #171
• Began writing backend unit tests
• Transitioned many functions from file name-based to UID-based (will help when we move to a real DB system)
• File sharing now works much more reliably
  • Fixes Can't share videos publicity when multi-user mode enabled #375
• Patches security issues with all non-dev backend and frontend dependencies
  • Closes Please stop using insecure dependencies. #367
• Fixes issue where audio player disappeared with certain browsers
  • Closes audio player UI disappears after loading #387

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Screenshots:

Database settings

Concurrent streams demo

111569899-4393af00-8769-11eb-9cb6-7b230e2c3a86.mp4