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/notes/notes.service.ts

@@ -182,7 +182,10 @@ export class NotesService {
    */
   async getNoteContent(note: Note): Promise<string> {
     return (
-      this.realtimeNoteStore.find(note.id)?.getYDoc().getCurrentContent() ??
+      this.realtimeNoteStore
+        .find(note.id)
+        ?.getRealtimeDoc()
+        .getCurrentContent() ??
       (await this.revisionsService.getLatestRevision(note)).content
     );
   }