Add EmailOut components: entity, DTO, repository, and services

- Introduced EmailOut and EmailOutDto for data management.
- Added EmailOutRepository and service interfaces based on CRUD patterns.

EnvelopeGenerator.Infrastructure/Contracts/IEmailOutRepository.cs

@@ -0,0 +1,9 @@
+using DigitalData.Core.Contracts.Infrastructure;
+using EnvelopeGenerator.Domain.Entities;
+
+namespace EnvelopeGenerator.Infrastructure.Contracts
+{
+    public interface IEmailOutRepository : ICRUDRepository<EmailOut, int>
+    {
+    }
+}