Fix MongoDb NodaTime deserialization issue

src/core/Elsa.Abstractions/Extensions/StateExtensions.cs

@@ -14,7 +14,11 @@ namespace Elsa.Extensions
         public static T GetState<T>(this JObject state, string key, Func<T> defaultValue = null)
         {
             var item = state.GetValue(key, StringComparison.OrdinalIgnoreCase);
-            return item != null && item.Type != JTokenType.Null ? item.ToObject<T>(Serializer) : defaultValue != null ? defaultValue() : default(T);
+
+            if (item == null || item.Type == JTokenType.Null)
+                return defaultValue != null ? defaultValue() : default;
+
+            return item.ToObject<T>(Serializer);
         }
         
         public static T GetState<T>(this JObject state, Type type, string key, Func<T> defaultValue = null)

src/core/Elsa.Abstractions/Serialization/IWorkflowSerializerProvider.cs

@@ -1,9 +1,10 @@
-using Newtonsoft.Json;
-
-namespace Elsa.Serialization
-{
-    public interface IWorkflowSerializerProvider
-    {
-        JsonSerializer CreateJsonSerializer();
-    }
+using Newtonsoft.Json;
+
+namespace Elsa.Serialization
+{
+    public interface IWorkflowSerializerProvider
+    {
+        JsonSerializerSettings CreateJsonSerializerSettings();
+        JsonSerializer CreateJsonSerializer();
+    }
 }

src/core/Elsa.Core/Serialization/WorkflowSerializerProvider.cs

@@ -7,6 +7,15 @@ namespace Elsa.Serialization
 {
     public class WorkflowSerializerProvider : IWorkflowSerializerProvider
     {
+        public JsonSerializerSettings CreateJsonSerializerSettings()
+        {
+            return new JsonSerializerSettings
+            {
+                NullValueHandling = NullValueHandling.Ignore,
+                ContractResolver = new CamelCasePropertyNamesContractResolver()
+            }.ConfigureForNodaTime(DateTimeZoneProviders.Tzdb);
+        }
+
         public JsonSerializer CreateJsonSerializer()
         {
             var jsonSerializer = new JsonSerializer();

src/persistence/Elsa.Persistence.MongoDb/Serialization/JObjectSerializer.cs

@@ -1,7 +1,10 @@
 using MongoDB.Bson;
 using MongoDB.Bson.Serialization;
 using MongoDB.Bson.Serialization.Serializers;
+using Newtonsoft.Json;
 using Newtonsoft.Json.Linq;
+using NodaTime;
+using NodaTime.Serialization.JsonNet;
 
 namespace Elsa.Persistence.MongoDb.Serialization
 {
@@ -10,7 +13,9 @@ namespace Elsa.Persistence.MongoDb.Serialization
         public override JObject Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
         {
             var document = BsonDocumentSerializer.Instance.Deserialize(context);
-            return JObject.Parse(document.ToString());
+            var settings = new JsonSerializerSettings().ConfigureForNodaTime(DateTimeZoneProviders.Tzdb);
+
+            return JsonConvert.DeserializeObject<JObject>(document.ToString(), settings);
         }
 
         public override void Serialize(BsonSerializationContext context, BsonSerializationArgs args, JObject value)