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>

commons/src/message-transporters/message.ts

@@ -0,0 +1,36 @@
+/*
+ * SPDX-FileCopyrightText: 2022 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+import { RealtimeUser, RemoteCursor } from './realtime-user.js'
+
+export enum MessageType {
+  NOTE_CONTENT_STATE_REQUEST = 'NOTE_CONTENT_STATE_REQUEST',
+  NOTE_CONTENT_UPDATE = 'NOTE_CONTENT_UPDATE',
+  PING = 'PING',
+  PONG = 'PONG',
+  METADATA_UPDATED = 'METADATA_UPDATED',
+  DOCUMENT_DELETED = 'DOCUMENT_DELETED',
+  SERVER_VERSION_UPDATED = 'SERVER_VERSION_UPDATED',
+  REALTIME_USER_STATE_SET = 'REALTIME_USER_STATE_SET',
+  REALTIME_USER_SINGLE_UPDATE = 'REALTIME_USER_SINGLE_UPDATE',
+  REALTIME_USER_STATE_REQUEST = 'REALTIME_USER_STATE_REQUEST',
+  READY = 'READY'
+}
+
+export interface MessagePayloads {
+  [MessageType.NOTE_CONTENT_STATE_REQUEST]: number[]
+  [MessageType.NOTE_CONTENT_UPDATE]: number[]
+  [MessageType.REALTIME_USER_STATE_SET]: RealtimeUser[]
+  [MessageType.REALTIME_USER_SINGLE_UPDATE]: RemoteCursor
+}
+
+export type Message<T extends MessageType> = T extends keyof MessagePayloads
+  ? {
+      type: T
+      payload: MessagePayloads[T]
+    }
+  : {
+      type: T
+    }