feat: Add ExtractPdfAttachments Application layer (Command/Handler/Validator merged)

DocumentOperator.Application/ExtractPdfAttachments/ExtractPdfAttachmentsCommand.cs

@@ -0,0 +1,43 @@
+using DocumentOperator.Application.Common.Interfaces;
+using FluentValidation;
+using MediatR;
+
+namespace DocumentOperator.Application.ExtractPdfAttachments;
+
+/// <summary>
+/// Command to extract all embedded files from a PDF document and return as ZIP archive.
+/// </summary>
+public record ExtractPdfAttachmentsCommand : IRequest<byte[]>
+{
+    /// <summary>
+    /// PDF document stream. Must be positioned at the beginning (Position = 0).
+    /// </summary>
+    public required Stream PdfStream { get; init; }
+}
+
+/// <summary>
+/// Handler for ExtractPdfAttachmentsCommand.
+/// Extracts all embedded files from PDF and returns as ZIP archive.
+/// </summary>
+public class ExtractPdfAttachmentsCommandHandler(IPdfProcessor pdfProcessor) 
+    : IRequestHandler<ExtractPdfAttachmentsCommand, byte[]>
+{
+    public async Task<byte[]> Handle(ExtractPdfAttachmentsCommand request, CancellationToken cancellationToken)
+    {
+        // Delegate to infrastructure layer
+        return await pdfProcessor.ExtractAttachmentsAsync(request.PdfStream);
+    }
+}
+
+/// <summary>
+/// Validator for ExtractPdfAttachmentsCommand.
+/// </summary>
+public class ExtractPdfAttachmentsCommandValidator : AbstractValidator<ExtractPdfAttachmentsCommand>
+{
+    public ExtractPdfAttachmentsCommandValidator()
+    {
+        RuleFor(x => x.PdfStream)
+            .NotNull()
+            .WithMessage("PDF stream is required");
+    }
+}