refactor(ModifyDocStatusCommandBase): remove ChangedWhen-property

EnvelopeGenerator.Application/DocStatus/Commands/CreateDocStatusCommand.cs

@@ -5,11 +5,6 @@
 /// </summary>
 public record CreateDocStatusCommand : ModifyDocStatusCommandBase
 {
-    /// <summary>
-    /// Gets timestamp when this record was added. Returns null.
-    /// </summary>
-    public override DateTime? ChangedWhen => null;
-
     /// <summary>
     /// Gets timestamp when this record was added. Returns the StatusChangedWhen value.
     /// </summary>

EnvelopeGenerator.Application/DocStatus/Commands/ModifyDocStatusCommandBase.cs

@@ -32,11 +32,6 @@ public abstract record ModifyDocStatusCommandBase
     /// </summary>
     public DateTime StatusChangedWhen { get; } = DateTime.Now;
 
-    /// <summary>
-    /// Gets timestamp when this record was added.
-    /// </summary>
-    public abstract DateTime? ChangedWhen { get; }
-
     /// <summary>
     /// Maps the current command to a new instance of the specified type.
     /// </summary>

EnvelopeGenerator.Application/DocStatus/Commands/UpdateDocStatusCommand.cs

@@ -10,5 +10,5 @@ public record UpdateDocStatusCommand : ModifyDocStatusCommandBase
     /// <summary>
     /// Gets timestamp when this record was added. Returns the StatusChangedWhen value.
     /// </summary>
-    public override DateTime? ChangedWhen => StatusChangedWhen;
+    public DateTime? ChangedWhen => StatusChangedWhen;
 }