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/Document.cs

@@ -1,4 +1,5 @@
-using EnvelopeGenerator.Domain.Interfaces;
+using System;
+using EnvelopeGenerator.Domain.Interfaces;
 using System.ComponentModel.DataAnnotations;
 using System.ComponentModel.DataAnnotations.Schema;
 #if NETFRAMEWORK
@@ -11,11 +12,11 @@ namespace EnvelopeGenerator.Domain.Entities
 #if NET
     ;
 #elif NETFRAMEWORK
-    {
+{
 #endif
 
 [Table("TBSIG_ENVELOPE_DOCUMENT", Schema = "dbo")]
-public class Document : IHasEnvelope
+public class Document : IHasEnvelope, IHasAddedWhen
 {
     public Document()
     {
@@ -36,9 +37,13 @@ public class Document : IHasEnvelope
         = 0;
 #endif
 
+    [Required]
+    [Column("ADDED_WHEN", TypeName = "datetime")]
+    public DateTime AddedWhen { get; set; }
+
     [Column("BYTE_DATA", TypeName = "varbinary(max)")]
     public byte[]
-#if NET
+#if nullable
         ?
 #endif
         ByteData { get; set; }
@@ -52,21 +57,21 @@ public class Document : IHasEnvelope
 
     [Column("FILENAME_ORIGINAL", TypeName = "nvarchar(256)")]
     public string
-#if NET
+#if nullable
         ?
 #endif
         FileNameOriginal { get; set; }
     #endregion
 
     public virtual List<Signature>
-#if NET
+#if nullable
         ?
 #endif
         Elements { get; set; }
 
     [ForeignKey("EnvelopeId")]
     public virtual Envelope
-#if NET
+#if nullable
         ?
 #endif
         Envelope { get; set; }