Fix : ListByBlockingActivityAsync() in documentDB persistance layer is not retrieving the blocked activities (#471)

src/core/Elsa.Abstractions/Models/BlockingActivity.cs

@@ -1,3 +1,5 @@
+using Newtonsoft.Json;
+
 namespace Elsa.Models
 {
     public class BlockingActivity
@@ -11,8 +13,11 @@ namespace Elsa.Models
             ActivityId = activityId;
             ActivityType = activityType;
         }
-        
+
+        [JsonProperty(PropertyName = "activityId")]
         public string ActivityId { get; set; }
+
+        [JsonProperty(PropertyName = "activityType")]
         public string ActivityType { get; set; }
     }
 }