many fixes and improvements - rework for modules/ and common/

feat(emailer): add Postmark and Resend providers

backend/Modules/Messaging/Data/Message.cs

@@ -0,0 +1,11 @@
+using System.ComponentModel.DataAnnotations;
+using Hutopy.Common.Domain;
+
+namespace Hutopy.Modules.Messaging.Data;
+
+public class Message : Entity
+{
+    public Guid SubjectId { get; set; }
+    public Guid? ParentId { get; set; }
+    [MaxLength(2048)] public required string Value { get; set; }
+}