refactor code to with user TwoFactorProviders

src/Core/Utilities/EnumKeyResolver.cs

@@ -0,0 +1,21 @@
+using Newtonsoft.Json.Serialization;
+using System;
+
+namespace Bit.Core.Utilities
+{
+    public class EnumKeyResolver<T> : DefaultContractResolver where T : struct
+    {
+        protected override JsonDictionaryContract CreateDictionaryContract(Type objectType)
+        {
+            var contract = base.CreateDictionaryContract(objectType);
+            var keyType = contract.DictionaryKeyType;
+
+            if(keyType.BaseType == typeof(Enum))
+            {
+                contract.DictionaryKeyResolver = propName => ((T)Enum.Parse(keyType, propName)).ToString();
+            }
+
+            return contract;
+        }
+    }
+}