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

feat(emailer): add Postmark and Resend providers

backend/Common/Domain/Entity.cs

@@ -0,0 +1,10 @@
+namespace Hutopy.Common.Domain;
+
+public abstract class Entity
+{
+    public Guid Id { get; init; }
+    public Guid CreatedBy { get; init; }
+    public DateTimeOffset CreatedAt { get; init; }
+    public Guid? DeletedBy { get; set; }
+    public DateTimeOffset? DeletedAt { get; set; }
+}