Refactor EnvelopeReceiver and History controllers

- Added using directive for EnvelopeGenerator.Domain.Constants.
- Updated ignore_statuses type in EnvelopeReceiverController.
- Improved resource management with using statements for SqlConnection and SqlCommand.
- Changed from Array.Empty<Signature>() to Enumerable.Empty<Signature>() for better performance.
- Simplified GetEnvelopeStatus method in HistoryController by using Status directly.

EnvelopeGenerator.GeneratorAPI/Controllers/HistoryController.cs

@@ -3,9 +3,8 @@ using MediatR;
 using Microsoft.AspNetCore.Authorization;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.Extensions.Caching.Memory;
-using EnvelopeGenerator.Domain;
 using EnvelopeGenerator.Application.Histories.Queries;
-using EnvelopeGenerator.Application.Extensions;
+using EnvelopeGenerator.Domain.Constants;
 
 namespace EnvelopeGenerator.GeneratorAPI.Controllers;
 
@@ -94,7 +93,7 @@ public class HistoryController : ControllerBase
     public IActionResult GetEnvelopeStatus([FromQuery] EnvelopeStatus? status = null)
     {
         return status is null
-            ? Ok(_memoryCache.GetEnumAsDictionary<EnvelopeStatus>("gen.api", Constants.Status.NonHist, Constants.Status.RelatedToFormApp))
+            ? Ok(_memoryCache.GetEnumAsDictionary<EnvelopeStatus>("gen.api", Status.NonHist, Status.RelatedToFormApp))
             : Ok(status.ToString());
     }