Refactor PDF signing logic and appearance handling

Refactored `Pkcs11Options` by removing `DefaultCertificationLevel` and improving property documentation. Replaced `VisualSignature` in `PdfSignOptionsDto` with `Appearance` using the new `PdfSignatureAppearanceDto` class, which encapsulates signature appearance details, including font and color settings.

Enhanced `PdfSignatureCertificationLevel` enum with more descriptive values and added XML documentation. Updated `IPdfDigitalSignatureService` to support optional signature images and removed redundant methods.

Refactored `PdfDigitalSignatureService` to streamline appearance handling, validate inputs, and improve maintainability. Removed unused methods and added support for `PdfSignatureAppearanceDto`.

Simplified `PdfSignatureController` by consolidating form properties into `PdfSignOptionsDto`. Improved code readability and flexibility while removing redundant logic.

EnvelopeGenerator.Application/Common/Configurations/Pkcs11Options.cs

@@ -91,9 +91,4 @@ public sealed class Pkcs11Options
     /// <c>true</c> uses <see cref="DateTimeOffset.UtcNow"/>, <c>false</c> uses <see cref="DateTimeOffset.Now"/>.
     /// </summary>
     public bool UseUtcSigningTime { get; set; } = true;
-
-    /// <summary>
-    /// Optional global default certification level used when request-level options do not specify a value.
-    /// </summary>
-    public PdfSignatureCertificationLevel? DefaultCertificationLevel { get; set; }
 }

EnvelopeGenerator.Application/Common/Dto/PdfSignOptionsDto.cs

@@ -50,5 +50,5 @@ public sealed record PdfSignOptionsDto
     /// <summary>
     /// 
     /// </summary>
-    public PdfVisualSignatureOptionsDto VisualSignature { get; set; } = null!;
+    public PdfSignatureAppearanceDto? Appearance { get; set; }
 }

EnvelopeGenerator.Application/Common/Dto/PdfSignatureAppearanceDto.cs

@@ -0,0 +1,61 @@
+namespace EnvelopeGenerator.Application.Common.Dto;
+
+/// <summary>
+/// 
+/// </summary>
+/// <param name="ImageBytes"></param>
+/// <param name="PageNumber"></param>
+/// <param name="Left"></param>
+/// <param name="Bottom"></param>
+/// <param name="Width"></param>
+/// <param name="Height"></param>
+/// <param name="ShowLabels"></param>
+/// <param name="ShowName"></param>
+/// <param name="ShowDate"></param>
+/// <param name="ShowReason"></param>
+/// <param name="ShowLocation"></param>
+/// <param name="ShowDistinguishedName"></param>
+/// <param name="DateTimeFormat"></param>
+public sealed record PdfSignatureAppearanceDto(
+    int PageNumber,
+    double Left,
+    double Bottom,
+    double Width,
+    double Height,
+    bool ShowLabels = false,
+    bool ShowName = false,
+    bool ShowDate = false,
+    bool ShowReason = false,
+    bool ShowLocation = false,
+    bool ShowDistinguishedName = false,
+    string DateTimeFormat = "dd.MM.yyyy HH:mm:ss zzz")
+{
+    /// <summary>
+    /// 
+    /// </summary>
+    /// <param name="FamilyName"></param>
+    /// <param name="Size"></param>
+    /// <param name="IsBold"></param>
+    /// <param name="IsItalic"></param>
+    /// <param name="IsUnderline"></param>
+    public sealed record FontDto(string FamilyName = "Helvetica", float Size = 10, bool IsBold = false, bool IsItalic = false, bool IsUnderline = false)
+    {
+        /// <summary>
+        /// 
+        /// </summary>
+        public RgbaColorDto Color { get; init; } = new();
+    }
+
+    /// <summary>
+    /// 
+    /// </summary>
+    /// <param name="R"></param>
+    /// <param name="G"></param>
+    /// <param name="B"></param>
+    public sealed record RgbaColorDto(double R = 0, double G = 0, double B = 0);
+
+    /// <summary>
+    /// 
+    /// </summary>
+    public FontDto Font { get; init; } = new();
+} 

EnvelopeGenerator.Application/Common/Dto/PdfVisualSignatureOptionsDto.cs

@@ -1,20 +0,0 @@
-namespace EnvelopeGenerator.Application.Common.Dto;
-
-/// <summary>
-/// 
-/// </summary>
-/// <param name="ImageBytes"></param>
-/// <param name="PageNumber"></param>
-/// <param name="Left"></param>
-/// <param name="Bottom"></param>
-/// <param name="Width"></param>
-/// <param name="Height"></param>
-/// <param name="ShowLabels"></param>
-public sealed record PdfVisualSignatureOptionsDto(
-    byte[] ImageBytes,
-    int PageNumber,
-    double Left,
-    double Bottom,
-    double Width,
-    double Height,
-    bool ShowLabels = false);

EnvelopeGenerator.Application/Common/Enums/PdfSignatureCertificationLevel.cs

@@ -1,9 +1,27 @@
 namespace EnvelopeGenerator.Application.Common.Enums;
 
+/// <summary>
+/// 
+/// </summary>
 public enum PdfSignatureCertificationLevel
 {
+    /// <summary>
+    /// All changes are allowed
+    /// </summary>
     NoCertification = 0,
-    NoChangesAllowed = 1,
-    FormFillingAndSigning = 2,
-    FormFillingAndAnnotations = 3
+
+    /// <summary>
+    /// No changes are allowed
+    /// </summary>
+    NoChangesAllowed,
+
+    /// <summary>
+    /// Allows users to fill in forms and sign the document.
+    /// </summary>
+    FillForms,
+
+    /// <summary>
+    /// Allows users to fill in forms, create, modify and delete annotations, and sign the document.
+    /// </summary>
+    FillFormsAndAnnotate
 }

EnvelopeGenerator.Application/Common/Interfaces/Services/IPdfDigitalSignatureService.cs

@@ -14,18 +14,9 @@ public interface IPdfDigitalSignatureService
     /// <param name="inputPdf">Source PDF content stream.</param>
     /// <param name="outputPdf">Destination stream for signed PDF output.</param>
     /// <param name="options">Optional signing options that map to PDF signature metadata fields.</param>
+    /// <param name="image">Optional image stream for signature appearance.</param>
     /// <param name="cancellationToken">Cancellation token for cooperative cancellation.</param>
-    Task SignPdfAsync(Stream inputPdf, Stream outputPdf, PdfSignOptionsDto? options = null, CancellationToken cancellationToken = default);
-
-    /// <summary>
-    /// Applies multiple signatures to the provided PDF in sequence and returns
-    /// the final signed PDF document.
-    /// </summary>
-    /// <param name="inputPdf">Source PDF content stream.</param>
-    /// <param name="outputPdf">Destination stream for signed PDF output.</param>
-    /// <param name="optionsList">Ordered signing options; one signature is applied per item.</param>
-    /// <param name="cancellationToken">Cancellation token for cooperative cancellation.</param>
-    Task SignPdfAsync(Stream inputPdf, Stream outputPdf, IReadOnlyList<PdfSignOptionsDto> optionsList, CancellationToken cancellationToken = default);
+    Task SignPdfAsync(Stream inputPdf, Stream outputPdf, PdfSignOptionsDto? options = null, Stream? image = null, CancellationToken cancellationToken = default);
 
     /// <summary>
     /// Checks whether the provided PDF contains signature field(s) and whether
@@ -35,13 +26,4 @@ public interface IPdfDigitalSignatureService
     /// <param name="cancellationToken">Cancellation token for cooperative cancellation.</param>
     /// <returns>A structured result containing signature presence and per-signature details.</returns>
     Task<PdfSignatureCheckResultDto> CheckPdfSignatureAsync(Stream inputPdf, CancellationToken cancellationToken = default);
-
-    /// <summary>
-    /// Extracts the original signed revision from a signed PDF.
-    /// For multi-revision files this returns the first signed revision bytes.
-    /// </summary>
-    /// <param name="inputPdf">Signed PDF content stream.</param>
-    /// <param name="outputPdf">Destination stream for original revision output.</param>
-    /// <param name="cancellationToken">Cancellation token for cooperative cancellation.</param>
-    Task ExtractOriginalPdfAsync(Stream inputPdf, Stream outputPdf, CancellationToken cancellationToken = default);
 }