Added ef core integration

debug/TestApplication/Models/Post.cs

@@ -0,0 +1,13 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace TestApplication.Models;
+
+public class Post {
+    [Key]
+    public Guid Id { get; } = Guid.CreateVersion7();
+    
+    public required User Sender { get; set; }
+    
+    [MaxLength(5000)]
+    public required string Message { get; set; }
+}