Allow [Parameter] to control JSON Field Names.

Previously, SimpleJsonSerializer.MapClrMemberNameToJsonFieldName
special cased the name "Links" since while that was the name of the
property in the object model, in JSON "_links" was used instead.

It turns out that there was an additional problem, where GitReference
wants to expose as Repository, but the name in JSON responses is
"repo".  Instead of simply adding another special case to
MapClrMemberNameToJsonFieldName, we update the implementation of the
serializer to allow [Parameter(Key = "some_name")] to denote what name
we'd like to use for the field in the JSON object when we serialize.

Octokit.Tests/SimpleJsonSerializerTests.cs

@@ -135,7 +135,7 @@ namespace Octokit.Tests
             }
 
             [Fact]
-            public void IgnoresUnderscore()
+            public void RespectsParameterKeyName()
             {
                 const string json = "{\"_links\":\"blah\"}";
 
@@ -151,6 +151,7 @@ namespace Octokit.Tests
             public string FirstName { get; set; }
             public bool IsSomething { get; set; }
             public bool Private { get; set; }
+            [Parameter(Key = "_links")]
             public string Links { get; set; }
         }
     }

Octokit/Http/SimpleJsonSerializer.cs

@@ -26,11 +26,17 @@ namespace Octokit.Internal
             readonly List<string> _membersWhichShouldPublishNull
                  = new List<string>();
 
-            protected override string MapClrMemberNameToJsonFieldName(string clrPropertyName)
+            protected override string MapClrMemberToJsonFieldName(MemberInfo member)
             {
-                var rubyCased = clrPropertyName.ToRubyCase();
-                if (rubyCased == "links") return "_links"; // Special case for GitHub API
-                return rubyCased;
+                var memberName = member.Name;
+                var paramAttr = member.GetCustomAttribute<ParameterAttribute>();
+
+                if (paramAttr != null && !string.IsNullOrEmpty(paramAttr.Key))
+                {
+                    memberName = paramAttr.Key;
+                }
+
+                return memberName.ToRubyCase();
             }
 
             internal override IDictionary<string, ReflectionUtils.GetDelegate> GetterValueFactory(Type type)
@@ -53,7 +59,7 @@ namespace Octokit.Internal
                     var attribute = propertyInfo.GetCustomAttribute<SerializeNullAttribute>();
                     if (attribute == null)
                         continue;
-                    _membersWhichShouldPublishNull.Add(fullName + MapClrMemberNameToJsonFieldName(propertyInfo.Name));
+                    _membersWhichShouldPublishNull.Add(fullName + MapClrMemberToJsonFieldName(propertyInfo));
                 }
                 foreach (var fieldInfo in ReflectionUtils.GetFields(type))
                 {
@@ -62,7 +68,7 @@ namespace Octokit.Internal
                     var attribute = fieldInfo.GetCustomAttribute<SerializeNullAttribute>();
                     if (attribute == null)
                         continue;
-                    _membersWhichShouldPublishNull.Add(fullName + MapClrMemberNameToJsonFieldName(fieldInfo.Name));
+                    _membersWhichShouldPublishNull.Add(fullName + MapClrMemberToJsonFieldName(fieldInfo));
                 }
 
                 return base.GetterValueFactory(type);
@@ -89,7 +95,7 @@ namespace Octokit.Internal
                                 continue;
                         }
 
-                        jsonObject.Add(MapClrMemberNameToJsonFieldName(getter.Key), value);
+                        jsonObject.Add(getter.Key, value);
                     }
                 }
                 output = jsonObject;

Octokit/Models/Response/Feed.cs

@@ -3,6 +3,7 @@ using System.Collections.Generic;
 using System.Diagnostics;
 using System.Globalization;
 using System.Threading.Tasks;
+using Octokit.Internal;
 
 namespace Octokit
 {
@@ -45,6 +46,7 @@ namespace Octokit
         /// <summary>
         /// List of feed urls including feed url and feed type, e.g. application/atom+xml
         /// </summary>
+        [Parameter(Key = "_links")]
         public FeedLinks Links { get; set; }
 
         internal string DebuggerDisplay