fix(PdfMergeBehavior): improve error diagnostics and exception messages in PdfMergeBehavior

- Added detailed request context to all MergeDocumentException messages
- Clarified conversion error message from "converted to PDF/A" to "converted to byte"
- Removed unused base64 conversion and redundant variable assignment
- Improved code readability and string concatenation formatting

EnvelopeGenerator.Application/Pdf/Behaviors/PdfMergeBehavior.cs

@@ -1,5 +1,4 @@
 #if WINDOWS
-using DevExpress.XtraReports;
 using EnvelopeGenerator.Application.Common.Extensions;
 using EnvelopeGenerator.Application.Exceptions;
 using EnvelopeGenerator.Domain.Constants;
@@ -26,9 +25,9 @@ public class PdfMergeBehavior : IPipelineBehavior<BurnPdfCommand, byte[]>
         var doc = await next(cancel);
 
         if (request.Report is null)
-            throw new InvalidOperationException("The final document report could not be merged." +
+            throw new InvalidOperationException("The final document report could not be merged." 
-            "There may be an error related to the behavior register order." +
+                + "There may be an error related to the behavior register order." 
-            "Request details:\n" + request.ToJson(Format.Json.ForDiagnostics));
+                + "Request details:\n" + request.ToJson(Format.Json.ForDiagnostics));
 
         using var oDocumentStream = new MemoryStream(doc);
         using var oReportStream = new MemoryStream(request.Report);
@@ -42,31 +41,31 @@ public class PdfMergeBehavior : IPipelineBehavior<BurnPdfCommand, byte[]>
 
         oStatus = oDocumentPDF.GetStat();
         if (oStatus != GdPictureStatus.OK)
-            throw new MergeDocumentException($"Document could not be loaded: {oStatus}");
+            throw new MergeDocumentException($"Document could not be loaded: {oStatus}." 
+                + "Request details:\n" + request.ToJson(Format.Json.ForDiagnostics));
 
         // Load the report file into memory
         oReportPDF.LoadFromStream(oReportStream, true);
         oStatus = oReportPDF.GetStat();
         if (oStatus != GdPictureStatus.OK)
-            throw new MergeDocumentException($"Report could not be loaded: {oStatus}");
+            throw new MergeDocumentException($"Report could not be loaded: {oStatus}." 
+                + "Request details:\n" + request.ToJson(Format.Json.ForDiagnostics));
 
         // Merge the documents 
         var oMergedPDF = oDocumentPDF.Merge2Documents(oDocumentPDF, oReportPDF);
         oStatus = oMergedPDF.GetStat();
         if (oStatus != GdPictureStatus.OK)
-            throw new MergeDocumentException($"Documents could not be merged: {oStatus}");
+            throw new MergeDocumentException($"Documents could not be merged: {oStatus}." 
+                + "Request details:\n" + request.ToJson(Format.Json.ForDiagnostics));
 
         // Convert to byte
         oMergedPDF.SaveToStream(oFinalStream);
         oStatus = oDocumentPDF.GetStat();
         if (oStatus != GdPictureStatus.OK)
-            throw new MergeDocumentException($"Document could not be converted to PDF/A: {oStatus}");
+            throw new MergeDocumentException($"Document could not be converted to byte: {oStatus}."
+                + "Request details:\n" + request.ToJson(Format.Json.ForDiagnostics));
 
-        doc = oFinalStream.ToArray();
+        return oFinalStream.ToArray();
-
-        string base64String = Convert.ToBase64String(doc);
-
-        return doc;
     }
 }
 #endif