Emit realtime chat messages from REST sends

src/modules/chat/chat-realtime.service.ts

@@ -0,0 +1,19 @@
+import { Injectable } from '@nestjs/common';
+import { Server } from 'socket.io';
+
+@Injectable()
+export class ChatRealtimeService {
+  private server?: Server;
+
+  bindServer(server: Server): void {
+    this.server = server;
+  }
+
+  emitNewMessage(conversationId: string, message: unknown): void {
+    this.server?.to(this.conversationRoom(conversationId)).emit('new_message', message);
+  }
+
+  private conversationRoom(conversationId: string): string {
+    return `conversation:${conversationId}`;
+  }
+}