feat(pdf): add annotation burning logic and repository dependency to BurnPdfCommandHandler

- Inject IRepository<Signature> for accessing signature and annotation data
- Implement BurnAnnotsToPDF method to process annotations from DB or JSON
- Add BurnElementAnnotsToPDF and BurnInstantJSONAnnotsToPDF stubs
- Integrate EF Core Include for loading related entities

EnvelopeGenerator.Application/Pdf/BurnPdfCommand.cs

@@ -1,6 +1,10 @@
-using EnvelopeGenerator.Application.Common.Configurations;
+using DigitalData.Core.Abstraction.Application.Repository;
+using DigitalData.Core.Abstractions;
+using EnvelopeGenerator.Application.Common.Configurations;
+using EnvelopeGenerator.Domain.Entities;
 using GdPicture14;
 using MediatR;
+using Microsoft.EntityFrameworkCore;
 
 namespace EnvelopeGenerator.Application.Pdf;
 
@@ -23,15 +27,54 @@ public class BurnPdfCommandHandler : IRequestHandler<BurnPdfCommand>
 
     private readonly AnnotationManager _manager;
 
+    private readonly IRepository<Signature> _signRepo;
+
     /// <summary>
     /// 
     /// </summary>
     /// <param name="pdfBurnerParams"></param>
     /// <param name="manager"></param>
-    public BurnPdfCommandHandler(PDFBurnerParams pdfBurnerParams, AnnotationManager manager)
+    /// <param name="signRepo"></param>
+    public BurnPdfCommandHandler(PDFBurnerParams pdfBurnerParams, AnnotationManager manager, IRepository<Signature> signRepo)
     {
         _pdfBurnerParams = pdfBurnerParams;
         _manager = manager;
+        _signRepo = signRepo;
+    }
+
+    public byte[] BurnAnnotsToPDF(byte[] pSourceBuffer, List<string> pInstantJSONList, int envelopeId)
+    {
+        // read the elements of envelope with their annotations
+        var elements = _signRepo
+            .Where(sig => sig.Document.EnvelopeId == envelopeId)
+            .Include(sig => sig.Annotations)
+            .ToList();
+
+        return elements.Any()
+            ? BurnElementAnnotsToPDF(pSourceBuffer, elements)
+            : BurnInstantJSONAnnotsToPDF(pSourceBuffer, pInstantJSONList);
+    }
+
+    /// <summary>
+    /// 
+    /// </summary>
+    /// <param name="pSourceBuffer"></param>
+    /// <param name="elements"></param>
+    /// <returns></returns>
+    public byte[] BurnElementAnnotsToPDF(byte[] pSourceBuffer, List<Signature> elements)
+    {
+        return Enumerable.Empty<byte>().ToArray();
+    }
+
+    /// <summary>
+    /// 
+    /// </summary>
+    /// <param name="pSourceBuffer"></param>
+    /// <param name="pInstantJSONList"></param>
+    /// <returns></returns>
+    public byte[] BurnInstantJSONAnnotsToPDF(byte[] pSourceBuffer, List<string> pInstantJSONList)
+    {
+        return Enumerable.Empty<byte>().ToArray();
     }
 
     /// <summary>