Add AutoMapper profile for entity self-mappings

Introduce `EntitySelfMappingProfile` to enable self-mappings (T -> T) for domain entities (`EmailAccount`, `ReceivedEmail`, `EmailAttachment`). This ensures uniform AutoMapper usage in the generic repository, regardless of whether the target type is a DTO or the entity itself. Added necessary `using` directives for `AutoMapper` and domain entities.

src/infrastructure/DigitalData.MessagingService.Infrastructure/DependencyInjection.cs

@@ -64,6 +64,9 @@ public static class DependencyInjection
 
         services.AddScoped(typeof(IRepository<>), typeof(Repository<>));
 
+        // AutoMapper - Register entity self-mappings (T -> T) for generic repository
+        services.AddAutoMapper(config => config.AddMaps(typeof(EntitySelfMappingProfile).Assembly));
+
         return services;
     }
 }

src/infrastructure/DigitalData.MessagingService.Infrastructure/Mappings/EntitySelfMappingProfile.cs

@@ -0,0 +1,19 @@
+using AutoMapper;
+using DigitalData.MessagingService.Domain.Entities;
+
+namespace DigitalData.MessagingService.Infrastructure.Mappings;
+
+/// <summary>
+/// AutoMapper profile that registers self-mappings (T -> T) for all domain entities.
+/// This allows AutoMapper to be used uniformly in the generic repository
+/// regardless of whether TDto is a DTO or the entity type itself.
+/// </summary>
+public class EntitySelfMappingProfile : Profile
+{
+    public EntitySelfMappingProfile()
+    {
+        CreateMap<EmailAccount, EmailAccount>();
+        CreateMap<ReceivedEmail, ReceivedEmail>();
+        CreateMap<EmailAttachment, EmailAttachment>();
+    }
+}