Adding chat system

Models/ChatMessage.cs

@@ -0,0 +1,19 @@
+using System;
+using MongoDB.Bson;
+using MongoDB.Bson.Serialization.Attributes;
+
+namespace GameAuthApi.Models;
+
+public class ChatMessage
+{
+    [BsonId]
+    [BsonRepresentation(BsonType.ObjectId)]
+    public string Id { get; set; }
+
+    [BsonRepresentation(BsonType.ObjectId)]
+    public string SenderId { get; set; }
+
+    public string Content { get; set; }
+
+    public DateTime Timestamp { get; set; } = DateTime.UtcNow;
+}