liowebrtc full mesh

The CRDT library y-js requires knowledge of all connected users (otherwise it rejects incoming messages). liowebrtc currently only tells us about connected peers, which – in partial mesh mode – are only the peers we are actually connected to. I have, therefore, temporarily disabled the partial mesh mode.

I also fixed a small bug in my adapter that caused initial sync requests to be lost (hence the sometimes missing synchronisation).

Lastly, I added lots of debug logging so that if we encounter further synchronisation bugs, I can investigate them on the deployment server.

@alh1717 @mnr17 Can we merge this to see if it works on deployment?