Add exception handling to EvaluateAsync method

The EvaluateAsync method in XmlTemplateReader class has been updated to handle exceptions. A new exception called TransformationEvaluationFailedException has been introduced and will be thrown when the evaluation of a transformation expression fails during the transformation of an XML document. Adjustments were also made to the TransformationFunctionMissingClosingBracketException class.

source/X39.Solutions.PdfTemplate/Xml/Exceptions/TransformationEvaluationFailedException.cs

@@ -0,0 +1,22 @@
+namespace X39.Solutions.PdfTemplate.Xml.Exceptions;
+
+/// <summary>
+/// Thrown when the evaluation of a transformation expression fails during the transformation of an XML document.
+/// </summary>
+public sealed class TransformationEvaluationFailedException : XmlTemplateTransformationException
+{
+    /// <summary>
+    /// Represents an expression used in XML template transformation.
+    /// </summary>
+    public string Expression { get; }
+
+    internal TransformationEvaluationFailedException(string expression, XmlNode node, Exception exception)
+        : base(
+            $"Failed to evaluate expression '{expression}' at L{node.Line}:C{node.Column} with exception: {exception.Message}",
+            exception,
+            node
+        )
+    {
+        Expression = expression;
+    }
+}

source/X39.Solutions.PdfTemplate/Xml/Exceptions/TransformationFunctionMissingClosingBracketException.cs

@@ -9,14 +9,17 @@ public sealed class TransformationFunctionMissingClosingBracketException : XmlTe
     /// The function text that failed to parse.
     /// </summary>
     public string FunctionText { get; }
-    
+
     /// <summary>
     /// The number of brackets that are missing.
     /// </summary>
-    public int    BracketsMissing { get; }
+    public int BracketsMissing { get; }
+
     internal TransformationFunctionMissingClosingBracketException(string text, XmlNode node, int bracketsMissing)
-        : base ($"Failed to parse function expression '{text}' at L{node.Line}:C{node.Column}, missing closing bracket (bracket count: {bracketsMissing}).",
-            node)
+        : base(
+            $"Failed to parse function expression '{text}' at L{node.Line}:C{node.Column}, missing closing bracket (bracket count: {bracketsMissing}).",
+            node
+        )
     {
         FunctionText    = text;
         BracketsMissing = bracketsMissing;

source/X39.Solutions.PdfTemplate/Xml/XmlTemplateReader.cs

@@ -93,9 +93,21 @@ private async Task<int> TransformNodeAsync(
             if (!value.StartsWith('@'))
                 continue;
             // Evaluate potential expressions
-            var result = await _templateData.EvaluateAsync(_cultureInfo, value[1..], cancellationToken)
-                                            .ConfigureAwait(false);
-            node.SetAttribute(key, result?.ToString() ?? string.Empty);
+            try
+            {
+                var result = await _templateData.EvaluateAsync(_cultureInfo, value[1..], cancellationToken)
+                                                .ConfigureAwait(false);
+
+                node.SetAttribute(key, result?.ToString() ?? string.Empty);
+            }
+            catch (Exception ex)
+            {
+                // Enrich the exception with additional information
+                throw new TransformationEvaluationFailedException(
+                    value,
+                    node,
+                    ex);
+            }
         }
         if (node is {IsTextNode: true, Text: { } text} && (text.Contains('@') || text.Contains('{')))
         {