Refactor Signature record and update EnvelopeReceiverController

- Removed default email assignment in Signature record.
- Eliminated unused using directive in EnvelopeReceiverController.
- Added new parameters for document execution and connection string options in the controller's constructor.

EnvelopeGenerator.GeneratorAPI/Controllers/EnvelopeReceiverController.cs

@@ -15,7 +15,6 @@ using Microsoft.AspNetCore.Mvc;
 using Microsoft.Data.SqlClient;
 using Microsoft.Extensions.Options;
 using System.Data;
-using System.Threading.Channels;
 
 namespace EnvelopeGenerator.GeneratorAPI.Controllers;
 
@@ -55,6 +54,8 @@ public class EnvelopeReceiverController : ControllerBase
     /// <param name="mapper"></param>
     /// <param name="envelopeExecutor"></param>
     /// <param name="erExecutor"></param>
+    /// <param name="documentExecutor"></param>
+    /// <param name="csOpt"></param>
     public EnvelopeReceiverController(ILogger<EnvelopeReceiverController> logger, IEnvelopeReceiverService envelopeReceiverService, IMediator mediator, IMapper mapper, IEnvelopeExecutor envelopeExecutor, IEnvelopeReceiverExecutor erExecutor, IDocumentExecutor documentExecutor, IOptions<ConnectionString> csOpt)
     {
         _logger = logger;