Refactor: Rename DocumentOperator to DocumentService

Updated project and solution files to rename and restructure
`DocumentOperator` to `DocumentService`. Modified project
references in `DocumentService.API.csproj`, `DocumentService.Application.csproj`,
and `DocumentService.Infrastructure.csproj` to reflect the new
naming convention. Updated `DocumentService.sln` to remove
old project references, add new ones, and adjust configuration
and nested project mappings accordingly. This change aligns
the project structure with the new naming convention.

DocumentService.API/Controllers/PdfValidationController.cs

@@ -0,0 +1,170 @@
+using DocumentService.Application.Common.DTOs;
+using DocumentService.Application.ValidatePdf.Queries;
+using DocumentService.Application.ValidatePdfA.Queries;
+using DocumentService.Client.Models.Requests;
+using DocumentService.Domain.Common.Exceptions;
+using MediatR;
+using Microsoft.AspNetCore.Mvc;
+
+namespace DocumentService.API.Controllers;
+
+/// <summary>
+/// PDF validation operations
+/// </summary>
+[ApiController]
+[Route("api/pdf/validation")]
+[Produces("application/json")]
+public class PdfValidationController(IMediator Mediator) : ControllerBase
+{
+    /// <summary>
+    /// Validates a PDF document and returns metadata (multipart/form-data)
+    /// </summary>
+    /// <param name="file">PDF file to validate</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>PDF metadata (page count, file size, PDF version, attachments)</returns>
+    /// <response code="200">PDF is valid, metadata returned</response>
+    /// <response code="400">Invalid PDF or file format</response>
+    /// <response code="500">Internal server error during validation</response>
+    [HttpPost("validate")]
+    [Consumes("multipart/form-data")]
+    [ProducesResponseType(typeof(PdfValidationResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> ValidateFromFile(
+        IFormFile file,
+        CancellationToken cancellationToken)
+    {
+        if (file == null || file.Length == 0)
+        {
+            return BadRequest(new ProblemDetails
+            {
+                Title = "Invalid file",
+                Detail = "File is required and cannot be empty",
+                Status = StatusCodes.Status400BadRequest
+            });
+        }
+
+        // Use IFormFile stream directly (no intermediate byte[] conversion)
+        using var pdfStream = file.OpenReadStream();
+        
+        // Direct pass-through to MediatR
+        var query = new ValidatePdfQuery { PdfStream = pdfStream };
+        var result = await Mediator.Send(query, cancellationToken);
+        
+        return Ok(result);
+    }
+
+    /// <summary>
+    /// Validates a PDF document and returns metadata (Base64 JSON)
+    /// </summary>
+    /// <param name="request">Request containing Base64-encoded PDF</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>PDF metadata (page count, file size, PDF version, attachments)</returns>
+    /// <response code="200">PDF is valid, metadata returned</response>
+    /// <response code="400">Invalid PDF or Base64 format</response>
+    /// <response code="500">Internal server error during validation</response>
+    [HttpPost("validate")]
+    [Consumes("application/json")]
+    [ProducesResponseType(typeof(PdfValidationResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> ValidateFromBase64(
+        [FromBody] ValidatePdfBase64Request request,
+        CancellationToken cancellationToken)
+    {
+        // Convert Base64 to stream (wrap in try-catch to throw BadRequestException)
+        byte[] pdfBytes;
+        try
+        {
+            pdfBytes = Convert.FromBase64String(request.Base64Pdf);
+        }
+        catch (FormatException ex)
+        {
+            throw new BadRequestException("Invalid Base64 format: " + ex.Message);
+        }
+        
+        using var pdfStream = new MemoryStream(pdfBytes);
+        
+        // Direct pass-through to MediatR
+        var query = new ValidatePdfQuery { PdfStream = pdfStream };
+        var result = await Mediator.Send(query, cancellationToken);
+        
+        return Ok(result);
+    }
+
+    /// <summary>
+    /// Validates a PDF/A document and checks conformance level (multipart/form-data)
+    /// </summary>
+    /// <param name="file">PDF file to validate</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>PDF/A metadata (conformance level, errors, warnings)</returns>
+    /// <response code="200">PDF/A validation completed, results returned</response>
+    /// <response code="400">Invalid PDF or file format</response>
+    /// <response code="500">Internal server error during validation</response>
+    [HttpPost("validate-pdfa")]
+    [Consumes("multipart/form-data")]
+    [ProducesResponseType(typeof(PdfAValidationResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> ValidatePdfAFromFile(
+        IFormFile file,
+        CancellationToken cancellationToken)
+    {
+        if (file == null || file.Length == 0)
+        {
+            return BadRequest(new ProblemDetails
+            {
+                Title = "Invalid file",
+                Detail = "File is required and cannot be empty",
+                Status = StatusCodes.Status400BadRequest
+            });
+        }
+
+        // Use IFormFile stream directly (no intermediate byte[] conversion)
+        using var pdfStream = file.OpenReadStream();
+        
+        // Direct pass-through to MediatR
+        var query = new ValidatePdfAQuery { PdfStream = pdfStream };
+        var result = await Mediator.Send(query, cancellationToken);
+        
+        return Ok(result);
+    }
+
+    /// <summary>
+    /// Validates a PDF/A document and checks conformance level (Base64 JSON)
+    /// </summary>
+    /// <param name="request">Request containing Base64-encoded PDF</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>PDF/A metadata (conformance level, errors, warnings)</returns>
+    /// <response code="200">PDF/A validation completed, results returned</response>
+    /// <response code="400">Invalid PDF or Base64 format</response>
+    /// <response code="500">Internal server error during validation</response>
+    [HttpPost("validate-pdfa")]
+    [Consumes("application/json")]
+    [ProducesResponseType(typeof(PdfAValidationResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> ValidatePdfAFromBase64(
+        [FromBody] ValidatePdfABase64Request request,
+        CancellationToken cancellationToken)
+    {
+        // Convert Base64 to stream (wrap in try-catch to throw BadRequestException)
+        byte[] pdfBytes;
+        try
+        {
+            pdfBytes = Convert.FromBase64String(request.Base64Pdf);
+        }
+        catch (FormatException ex)
+        {
+            throw new BadRequestException("Invalid Base64 format: " + ex.Message);
+        }
+        
+        using var pdfStream = new MemoryStream(pdfBytes);
+        
+        // Direct pass-through to MediatR
+        var query = new ValidatePdfAQuery { PdfStream = pdfStream };
+        var result = await Mediator.Send(query, cancellationToken);
+        
+        return Ok(result);
+    }
+}