add http status code to schematron validation

Author: ipax77

src/pax.XRechnung.NET/InvoiceValidationResult.cs

@@ -27,6 +27,10 @@ public InvoiceValidationResult(ICollection<ValidationEventArgs> validationEventA
         }
     }
     /// <summary>
+    /// HttpStatusCode
+    /// </summary>
+    public string HttpStatusCode { get; set; } = string.Empty;
+    /// <summary>
     /// Constructor
     /// </summary>
     /// <param name="validationMessages"></param>

src/pax.XRechnung.NET/XmlInvoiceVlidator.Schematron.cs

@@ -82,11 +82,12 @@ private static InvoiceValidationResult MapToValidationResult(SchematronValidatio
 
         if (!string.IsNullOrEmpty(kositResult.Error) || !kositResult.IsValid)
         {
-            validationEvents.Add(new(new XmlSchemaException("xml invalid"), kositResult.Error ?? "Unexpected error.", XmlSeverityType.Error));
+            validationEvents.Add(new(new XmlSchemaException("unknown"), kositResult.Error ?? kositResult.HttpStatusCode.ToString(), XmlSeverityType.Error));
         }
 
         var result = new InvoiceValidationResult(validationEvents)
         {
+            HttpStatusCode = kositResult.HttpStatusCode.ToString(),
             Evaluation = kositResult.Evaluation,
             Conformity = kositResult.Conformity
         };