Add audit interfaces and fields to domain entities

Introduced interfaces for audit fields (AddedWhen, ChangedWhen, ChangedWho, AddedWho) and updated domain entities to implement them. Adjusted properties for consistency and nullability. Updated MappingProfile to map audit fields between DTOs and entities. Improves auditability and standardization across the domain model.

EnvelopeGenerator.Domain/Entities/History.cs

@@ -1,24 +1,20 @@
-using DigitalData.UserManager.Domain.Entities;
+using System;
+using DigitalData.UserManager.Domain.Entities;
 using System.ComponentModel.DataAnnotations;
 using System.ComponentModel.DataAnnotations.Schema;
 using EnvelopeGenerator.Domain.Interfaces;
 using EnvelopeGenerator.Domain.Constants;
 using DigitalData.Core.Abstractions.Interfaces;
 
-
-#if NETFRAMEWORK
-using System;
-#endif
-
 namespace EnvelopeGenerator.Domain.Entities
 #if NET
     ;
 #elif NETFRAMEWORK
-    {
+{
 #endif
 
 [Table("TBSIG_ENVELOPE_HISTORY", Schema = "dbo")]
-public class History : IHasEnvelope, IHasReceiver, IEntity
+public class History : IHasEnvelope, IHasReceiver, IEntity, IHasAddedWhen, IHasChangedWhen
 {
     [Key]
     [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
@@ -43,7 +39,7 @@ public class History : IHasEnvelope, IHasReceiver, IEntity
     public DateTime AddedWhen { get; set; }
 
     [Column("ACTION_DATE", TypeName = "datetime")]
-    public DateTime? ActionDate { get; set; } = DateTime.Now;
+    public DateTime? ChangedWhen { get; set; }
     
     [Column("COMMENT", TypeName = "nvarchar(max)")]
     public string