Implement GetOrCreateApplicationAuthentication

Implements the endpoint for creating an application authorization token.

Octokit/Exceptions/TwoFactorRequiredException.cs

@@ -0,0 +1,55 @@
+using System;
+using System.Diagnostics.CodeAnalysis;
+using System.Runtime.Serialization;
+
+namespace Octokit
+{
+#if !NETFX_CORE
+    [Serializable]
+#endif
+    public class TwoFactorRequiredException : AuthorizationException
+    {
+        public TwoFactorRequiredException()
+        {
+        }
+
+        public TwoFactorRequiredException(string message) : base(message)
+        {
+        }
+
+        public TwoFactorRequiredException(string message, Exception innerException) : base(message, innerException)
+        {
+        }
+
+        public TwoFactorRequiredException(string message, TwoFactorType twoFactorType)
+            : base(message)
+        {
+            TwoFactorType = twoFactorType;
+        }
+
+#if !NETFX_CORE
+        protected TwoFactorRequiredException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+            if (info == null) return;
+            TwoFactorType = (TwoFactorType) (info.GetInt32("TwoFactorType"));
+        }
+
+        public override void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            base.GetObjectData(info, context);
+            info.AddValue("TwoFactorType", TwoFactorType);
+        }
+#endif
+
+        public TwoFactorType TwoFactorType { get; private set; }
+    }
+
+    public enum TwoFactorType
+    {
+        None,
+        Unknown,
+        [SuppressMessage("Microsoft.Naming", "CA1704:IdentifiersShouldBeSpelledCorrectly", MessageId = "Sms")] Sms,
+        AuthenticatorApp
+    }
+}