Updated the project file to support multi-targeting for both
.NET Framework 4.6.2 and .NET 8.0 by replacing `<TargetFramework>`
with `<TargetFrameworks>`.
Reformatted `AuthenticationFailedException` and
`NotFoundException` classes to use braces `{ }` for namespaces
and constructors for consistency. No functional changes were made
to the exception classes.
Significantly restructured the `DigitalData.MessagingService.Domain` project by removing unused domain-specific classes, enums, and value objects. Key changes include:
- Updated `ExceptionHandlingMiddleware` to handle `FluentValidation.ValidationException` with formatted validation errors mapped to `HttpStatusCode.BadRequest`.
- Removed foundational domain classes such as `BaseEntity`, `ValueObject`, and `IAggregateRoot`.
- Deleted enums (`AttachmentStatus`, `AuthenticationType`, `EmailStatus`, `ErrorCode`, `ProcessType`) and domain exceptions (`DomainException`, `AttachmentProcessingException`, `DmsNotAvailableException`, `InvalidPdfException`, `ValidationException`).
- Removed value objects (`EmailAddress`, `MessageId`) and the `MessageIdGenerator` service.
- Cleaned up the project structure by removing the `Events` folder reference.
These changes simplify the domain model, reduce unused code, and align the project with updated architectural goals.
