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/PdfConversionController.cs

@@ -0,0 +1,182 @@
+using DocumentService.Application.ConvertFromPdfA;
+using DocumentService.Application.ConvertToPdfA;
+using DocumentService.Client.Models.Requests;
+using DocumentService.Domain.Common.Exceptions;
+using MediatR;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Mvc;
+
+namespace DocumentService.API.Controllers;
+
+/// <summary>
+/// Controller for PDF conversion operations (PDF ? PDF/A)
+/// </summary>
+[ApiController]
+[Route("api/pdf/conversion")]
+[Obsolete("This endpoint is not implemented yet.")]
+public class PdfConversionController(IMediator mediator) : ControllerBase
+{
+    /// <summary>
+    /// Converts a standard PDF to PDF/A format.
+    /// Supports multipart/form-data file upload.
+    /// </summary>
+    /// <param name="file">The PDF file to convert</param>
+    /// <param name="pdfALevel">Target PDF/A level (e.g., "PDF/A-1b", "PDF/A-2b", "PDF/A-3b")</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>PDF/A compliant document</returns>
+    /// <response code="200">PDF converted to PDF/A successfully</response>
+    /// <response code="400">Invalid input (file missing, not a PDF, or invalid PDF/A level)</response>
+    /// <response code="500">Internal server error during PDF processing</response>
+    [Obsolete("This endpoint is not implemented yet.")]
+    [HttpPost("to-pdfa")]
+    [Consumes("multipart/form-data")]
+    [ProducesResponseType(typeof(FileContentResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> ConvertToPdfAFromFile(
+        IFormFile file,
+        [FromQuery] string pdfALevel = "PDF/A-3b",
+        CancellationToken cancellationToken = default)
+    {
+        if (file == null || file.Length == 0)
+        {
+            throw new BadRequestException("PDF file is required");
+        }
+
+        // Use IFormFile stream directly (no intermediate byte[] conversion)
+        using var pdfStream = file.OpenReadStream();
+
+        // Send command to MediatR
+        var command = new ConvertToPdfACommand 
+        { 
+            PdfStream = pdfStream,
+            PdfALevel = pdfALevel
+        };
+        byte[] resultPdf = await mediator.Send(command, cancellationToken);
+
+        // Return PDF/A file
+        return File(resultPdf, "application/pdf", "converted-pdfa.pdf");
+    }
+
+    /// <summary>
+    /// Converts a standard PDF to PDF/A format.
+    /// Supports Base64-encoded PDF via JSON payload.
+    /// </summary>
+    /// <param name="request">Request containing Base64-encoded PDF and PDF/A level</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>PDF/A compliant document</returns>
+    /// <response code="200">PDF converted to PDF/A successfully</response>
+    /// <response code="400">Invalid input (Base64 format error, not a PDF, or invalid PDF/A level)</response>
+    /// <response code="500">Internal server error during PDF processing</response>
+    [Obsolete("This endpoint is not implemented yet.")]
+    [HttpPost("to-pdfa")]
+    [Consumes("application/json")]
+    [ProducesResponseType(typeof(FileContentResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> ConvertToPdfAFromBase64(
+        [FromBody] ConvertToPdfARequest request,
+        CancellationToken cancellationToken = default)
+    {
+        // Convert Base64 PDF to stream
+        byte[] pdfBytes;
+        try
+        {
+            pdfBytes = Convert.FromBase64String(request.Base64Pdf);
+        }
+        catch (FormatException ex)
+        {
+            throw new BadRequestException("Invalid Base64 PDF format: " + ex.Message);
+        }
+        
+        using var pdfStream = new MemoryStream(pdfBytes);
+
+        // Send command to MediatR
+        var command = new ConvertToPdfACommand 
+        { 
+            PdfStream = pdfStream,
+            PdfALevel = request.PdfALevel ?? "PDF/A-3b"
+        };
+        byte[] resultPdf = await mediator.Send(command, cancellationToken);
+
+        // Return PDF/A file
+        return File(resultPdf, "application/pdf", "converted-pdfa.pdf");
+    }
+
+    /// <summary>
+    /// Converts a PDF/A document to a standard PDF (removes PDF/A restrictions).
+    /// Supports multipart/form-data file upload.
+    /// </summary>
+    /// <param name="file">The PDF/A file to convert</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>Standard PDF document</returns>
+    /// <response code="200">PDF/A converted to standard PDF successfully</response>
+    /// <response code="400">Invalid input (file missing, not a PDF)</response>
+    /// <response code="500">Internal server error during PDF processing</response>
+    [Obsolete("This endpoint is not implemented yet.")]
+    [HttpPost("from-pdfa")]
+    [Consumes("multipart/form-data")]
+    [ProducesResponseType(typeof(FileContentResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> ConvertFromPdfAFromFile(
+        IFormFile file,
+        CancellationToken cancellationToken = default)
+    {
+        if (file == null || file.Length == 0)
+        {
+            throw new BadRequestException("PDF/A file is required");
+        }
+
+        // Use IFormFile stream directly (no intermediate byte[] conversion)
+        using var pdfStream = file.OpenReadStream();
+
+        // Send command to MediatR
+        var command = new ConvertFromPdfACommand { PdfStream = pdfStream };
+        byte[] resultPdf = await mediator.Send(command, cancellationToken);
+
+        // Return standard PDF file
+        return File(resultPdf, "application/pdf", "converted-pdf.pdf");
+    }
+
+    /// <summary>
+    /// Converts a PDF/A document to a standard PDF (removes PDF/A restrictions).
+    /// Supports Base64-encoded PDF via JSON payload.
+    /// </summary>
+    /// <param name="request">Request containing Base64-encoded PDF/A</param>
+    /// <param name="cancellationToken">Cancellation token</param>
+    /// <returns>Standard PDF document</returns>
+    /// <response code="200">PDF/A converted to standard PDF successfully</response>
+    /// <response code="400">Invalid input (Base64 format error, not a PDF)</response>
+    /// <response code="500">Internal server error during PDF processing</response>
+    [Obsolete("This endpoint is not implemented yet.")]
+    [HttpPost("from-pdfa")]
+    [Consumes("application/json")]
+    [ProducesResponseType(typeof(FileContentResult), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status400BadRequest)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status500InternalServerError)]
+    public async Task<IActionResult> ConvertFromPdfAFromBase64(
+        [FromBody] ConvertFromPdfARequest request,
+        CancellationToken cancellationToken = default)
+    {
+        // Convert Base64 PDF to stream
+        byte[] pdfBytes;
+        try
+        {
+            pdfBytes = Convert.FromBase64String(request.Base64Pdf);
+        }
+        catch (FormatException ex)
+        {
+            throw new BadRequestException("Invalid Base64 PDF format: " + ex.Message);
+        }
+        
+        using var pdfStream = new MemoryStream(pdfBytes);
+
+        // Send command to MediatR
+        var command = new ConvertFromPdfACommand { PdfStream = pdfStream };
+        byte[] resultPdf = await mediator.Send(command, cancellationToken);
+
+        // Return standard PDF file
+        return File(resultPdf, "application/pdf", "converted-pdf.pdf");
+    }
+}