v3 - WIP

[janthurau]

goals:

• ⏳ Separate connection / provider more, make it more easy and remove weird hacks that were added to keep BC with v1
• ✅ Separate Hocuspocus server / handler logic
• subdocs support
• fix other breaking issues (#606)
• maybe we can implement reauthentication (not sure what's needed there ; maybe the provider can just re-send the info, but I think the server needs to be adjusted to handle the incoming message type)
• maybe we can finally upgrade ioredis (https://github.com/ueberdosis/hocuspocus/pull/580)
• https://github.com/ueberdosis/hocuspocus/issues/596
• https://github.com/ueberdosis/hocuspocus/issues/594
• ... (more to come)

[solirpa]

Consider using the api Y.diffUpdate, we don't need to load ydoc into memory.

Here is the simulation syncstep1 and syncstep2 code:

if messageYjsSyncStep1
    cli_sv = decode(cli_msg)
    srv_state = load(name)

    diff = Y.diffUpdate(srv_state, cli_sv);
    send(writeSyncStep2(diff))

    srv_sv = Y.encodeStateVectorFromUpdate(srv_state)
    send(writeFirstSyncStep(srv_sv))

else if messageYjsSyncStep2
    update = decode(msg)
    srv.persist(update)

......