Support for xml namespaces in XPathMatcher (#1005)

* Support for xml namespaces in XPathMatcher

* Review findings of Stef implemented.

* Fix of build error

* New review findings by Stef

---------

Co-authored-by: Carsten Alder <carsten.alder@schleupen.de>

src/WireMock.Net.Abstractions/Admin/Mappings/MatcherModel.cs

@@ -73,4 +73,8 @@ public class MatcherModel
     /// </summary>
     public MatcherModel? ContentMatcher { get; set; }
     #endregion
+
+    #region XPathMatcher
+    public XmlNamespace[]? XmlNamespaceMap { get; set; }
+    #endregion
 }

src/WireMock.Net.Abstractions/Admin/Mappings/XmlNamespace.cs

@@ -0,0 +1,21 @@
+namespace WireMock.Admin.Mappings;
+
+/// <summary>
+/// Defines an xml namespace consisting of prefix and uri.
+/// <example>xmlns:i="http://www.w3.org/2001/XMLSchema-instance"</example>
+/// </summary>
+[FluentBuilder.AutoGenerateBuilder]
+public class XmlNamespace
+{
+    /// <summary>
+    /// The prefix.
+    /// <example>i</example>
+    /// </summary>
+    public string Prefix { get; set; } = null!;
+
+    /// <summary>
+    /// The uri.
+    /// <example>http://www.w3.org/2001/XMLSchema-instance</example>
+    /// </summary>
+    public string Uri { get; set; } = null!;
+}