refactor: reimplement realtime-communication

This commit refactors a lot of things that are not easy to separate.
It replaces the binary protocol of y-protocols with json.
It introduces event based message processing.
It implements our own code mirror plugins for synchronisation of content and remote cursors

Signed-off-by: Tilman Vatteroth <git@tilmanvatteroth.de>

backend/src/realtime/realtime-note/realtime-note.service.ts

@@ -42,7 +42,7 @@ export class RealtimeNoteService implements BeforeApplicationShutdown {
     this.revisionsService
       .createRevision(
         realtimeNote.getNote(),
-        realtimeNote.getYDoc().getCurrentContent(),
+        realtimeNote.getRealtimeDoc().getCurrentContent(),
       )
       .catch((reason) => this.logger.error(reason));
   }