Add IHasChangedWhen support and cleanup using statements

Introduced IHasChangedWhen interface to EnvelopeReceiver and History.
Added HasEmailAndName property to EnvelopeReceiver.
Updated AutoMapperAuditingExtensions to map ChangedWhen to UTC.
Removed redundant using statements and fixed formatting.

EnvelopeGenerator.Application/Common/Extensions/AutoMapperAuditingExtensions.cs

@@ -1,4 +1,3 @@
-using System;
 using AutoMapper;
 using EnvelopeGenerator.Domain.Interfaces.Auditing;
 
@@ -22,4 +21,4 @@ public static class AutoMapperAuditingExtensions
     public static IMappingExpression<TSource, TDestination> MapChangedWhen<TSource, TDestination>(this IMappingExpression<TSource, TDestination> expression)
         where TDestination : IHasChangedWhen
         => expression.ForMember(dest => dest.ChangedWhen, opt => opt.MapFrom(_ => DateTime.UtcNow));
-}
+}