Refactor enum usage in codebase

Updated references from `Constants` to direct usage of `EnvelopeStatus` and `EmailTemplateType` enums. This change enhances code readability and reduces dependency on the `Constants` class.

Modified properties and parameters across command classes, DTOs, repositories, and services to use the enums directly. Updated `ModifyDocStatusCommandBase`, `EnvelopeHistoryDto`, and `ResetEmailTemplateCommand` for improved clarity.

Consistent updates across multiple files indicate a systematic refactoring aimed at streamlining the codebase and improving maintainability. Comments and documentation have also been revised to reflect these changes.

EnvelopeGenerator.Application/Interfaces/Services/IEnvelopeMailService.cs

@@ -2,7 +2,7 @@
 using DigitalData.EmailProfilerDispatcher.Abstraction.Contracts;
 using EnvelopeGenerator.Application.Dto.EnvelopeReceiver;
 using EnvelopeGenerator.Application.Dto.EnvelopeReceiverReadOnly;
-using EnvelopeGenerator.Domain;
+using EnvelopeGenerator.Domain.Constants;
 
 namespace EnvelopeGenerator.Application.Interfaces.Services;
 
@@ -19,7 +19,7 @@ public interface IEnvelopeMailService : IEmailOutService
     /// <param name="tempType"></param>
     /// <param name="optionalPlaceholders"></param>
     /// <returns></returns>
-    Task<DataResult<int>> SendAsync(EnvelopeReceiverDto envelopeReceiverDto, Constants.EmailTemplateType tempType, Dictionary<string, object>? optionalPlaceholders = null);
+    Task<DataResult<int>> SendAsync(EnvelopeReceiverDto envelopeReceiverDto, EmailTemplateType tempType, Dictionary<string, object>? optionalPlaceholders = null);
 
     /// <summary>
     ///