adding message model

models/message.ts

@@ -0,0 +1,15 @@
+import { Timestamp } from "firebase/firestore";
+
+export class Message {
+  id: string;
+  audioDataUrl: string;
+
+  senderUserId: string;
+  receiverUserId: string;
+
+  senderReceiver: string[]; // composite to make querying easier in the future
+
+  createdDate: Timestamp;
+
+  // firstListenDate: Timestamp;
+}