fix: serialize enumerable properties

#18

Author: OlivierAtSIEN

.npmrc

@@ -3,6 +3,7 @@
 using Newtonsoft.Json;
 using Newtonsoft.Json.Serialization;
 using System;
+using System.Collections;
 using System.Reflection;
 
 namespace Aguacongas.AspNetCore.Authentication
@@ -29,7 +30,7 @@ protected override JsonProperty CreateProperty(MemberInfo member, MemberSerializ
             var property = base.CreateProperty(member, memberSerialization);
             var propertyInfo = member as PropertyInfo;
             var propertyType = propertyInfo?.PropertyType;
-            property.ShouldSerialize = instance => propertyType != null && !propertyType.IsInterface && propertyInfo.CanWrite && !propertyType.IsSubclassOf(typeof(Delegate));
+            property.ShouldSerialize = instance => propertyType != null && (!propertyType.IsInterface || typeof(IEnumerable).IsAssignableFrom(propertyType)) && !propertyType.IsSubclassOf(typeof(Delegate));
 
             return property;
         }        

src/Aguacongas.AspNetCore.Authentication/ContractResolver.cs

@@ -0,0 +1,27 @@
+using Microsoft.AspNetCore.Authentication.OAuth;
+using Xunit;
+
+namespace Aguacongas.AspNetCore.Authentication.Test
+{
+    public class AuthenticationSchemeOptionsSerializerTest
+    {
+        [Fact]
+        public void SerializeOptions_should_serialize_OAuthOptionsScope()
+        {
+            var oAuthOptions = new OAuthOptions
+            {
+                ClientId = "test",
+            };
+
+            oAuthOptions.Scope.Add("test");
+
+            var sut = new AuthenticationSchemeOptionsSerializer();
+
+            var result = sut.SerializeOptions(oAuthOptions, typeof(OAuthOptions));
+
+            var expected = sut.DeserializeOptions(result, typeof(OAuthOptions)) as OAuthOptions;
+
+            Assert.Contains(expected.Scope, value => value == "test");
+        }
+    }
+}