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

feat(emailer): add Postmark and Resend providers

backend/Modules/Messaging/Models/MessageDto.cs

@@ -0,0 +1,12 @@
+namespace Hutopy.Modules.Messaging.Models;
+
+public record struct MessageDto(
+    Guid Id,
+    Guid SubjectId,
+    Guid CreatedBy,
+    string CreatedByName,
+    string? CreatedByPortraitUrl,
+    DateTimeOffset CreatedAt,
+    Guid? ParentId,
+    string Value
+);