feat: add message center

packages/data-center/src/message/code.ts

@@ -0,0 +1,3 @@
+export enum MessageCode {
+  loginError,
+}

packages/data-center/src/message/index.ts

@@ -0,0 +1,2 @@
+export { MessageCenter } from './message';
+export { MessageCode } from './code';

packages/data-center/src/message/message.ts

@@ -0,0 +1,24 @@
+import { Observable } from 'lib0/observable';
+import { Message } from 'src/types';
+import { MessageCode } from './code';
+
+export class MessageCenter extends Observable<string> {
+  constructor() {
+    super();
+  }
+
+  public send(message: MessageCode) {
+    this.emit('message', [message]);
+  }
+
+  public onMessage(callback: (message: Message) => void) {
+    this.on('message', callback);
+  }
+
+  private messages: Record<number, Message> = {
+    [MessageCode.loginError]: {
+      code: MessageCode.loginError,
+      message: 'Login failed',
+    },
+  };
+}