Update REST Admin interface to support "Get Mapping(s) as C# Code" (#878)

* Add /__admin/mappings/code endpoint

* api

* fix

* .

* fix

* .

* .

* .

src/WireMock.Net/MappingBuilder.cs

@@ -1,4 +1,6 @@
+using System;
 using System.Linq;
+using System.Text;
 using Newtonsoft.Json;
 using Stef.Validation;
 using WireMock.Admin.Mappings;
@@ -7,6 +9,7 @@ using WireMock.Owin;
 using WireMock.Serialization;
 using WireMock.Server;
 using WireMock.Settings;
+using WireMock.Types;
 using WireMock.Util;
 
 namespace WireMock;
@@ -66,10 +69,12 @@ public class MappingBuilder : IMappingBuilder
     /// <inheritdoc />
     public MappingModel[] GetMappings()
     {
-        return _options.Mappings.Values.ToArray()
-            .Where(m => !m.IsAdminInterface)
-            .Select(_mappingConverter.ToMappingModel)
-            .ToArray();
+        return GetMappingsInternal().Select(_mappingConverter.ToMappingModel).ToArray();
+    }
+
+    internal IMapping[] GetMappingsInternal()
+    {
+        return _options.Mappings.Values.ToArray().Where(m => !m.IsAdminInterface).ToArray();
     }
 
     /// <inheritdoc />
@@ -78,6 +83,37 @@ public class MappingBuilder : IMappingBuilder
         return ToJson(GetMappings());
     }
 
+    /// <inheritdoc />
+    public string? ToCSharpCode(Guid guid, MappingConverterType converterType)
+    {
+        var mapping = GetMappingsInternal().FirstOrDefault(m => m.Guid == guid);
+        if (mapping is null)
+        {
+            return null;
+        }
+
+        var settings = new MappingConverterSettings { AddStart = true, ConverterType = converterType };
+        return _mappingConverter.ToCSharpCode(mapping, settings);
+    }
+
+    /// <inheritdoc />
+    public string ToCSharpCode(MappingConverterType converterType)
+    {
+        var sb = new StringBuilder();
+        bool addStart = true;
+        foreach (var mapping in GetMappingsInternal())
+        {
+            sb.AppendLine(_mappingConverter.ToCSharpCode(mapping, new MappingConverterSettings { AddStart = addStart, ConverterType = converterType }));
+
+            if (addStart)
+            {
+                addStart = false;
+            }
+        }
+
+        return sb.ToString();
+    }
+
     /// <inheritdoc />
     public void SaveMappingsToFile(string path)
     {