Добавил search модель письма

SecuritySystem/SecuritySystemContracts/SearchModels/MessageInfoSearchModel.cs

@@ -0,0 +1,8 @@
+namespace SecuritySystemContracts.SearchModels
+{
+    public class MessageInfoSearchModel
+    {
+        public string? MessageId { get; set; }
+        public int? ClientId { get; set; }
+    }
+}