Enhance envelope creation functionality and configuration

- Updated DependencyInjection to include new command handler.
- Modified CreateEnvelopeReceiverCommand for nullable responses.
- Altered SQL command in EnvelopeReceiverAddReadSQL.
- Refactored EnvelopeReceiverController with new dependencies and improved CreateAsync method.
- Expanded appsettings.json with additional configuration settings.
- Introduced new DTOs for signatures and receivers in CreateEnvelopeReceiverDtos.

EnvelopeGenerator.Application/SQL/EnvelopeReceiverAddReadSQL.cs

@@ -14,12 +14,9 @@ public class EnvelopeReceiverAddReadSQL : ISQL<Envelope>
     /// </summary>
     public string Raw => @"
 		USE [DD_ECM]
-		GO
 
 		DECLARE	@OUT_RECEIVER_ID int
 
-		DECLARE	@ENV_UID varchar(36) = @ENV_UID
-
 		EXEC	[dbo].[PRSIG_API_CREATE_RECEIVER]
 				@ENV_UID = @ENV_UID,
 				@EMAIL_ADRESS = @EMAIL_ADRESS ,