refactor and add using constants instead of hard coded strings ...

Providers/GraphQL/XWebinarSubscriberGraphQLTypeHelper.cs

@@ -1,6 +1,7 @@
 using System;
 using xDataService.Configuration;
 using xDataService.GraphQL;
+using xWebinarService.Constants;
 using xWebinarService.Interfaces.Entities;
 using xWebinarService.Models.Entities;
 
@@ -15,12 +16,12 @@ namespace xWebinarService.Providers.GraphQL
 
         public override string GetInQueryCollectionName()
         {
-            return "webinarSubscribers";
+            return XWebinarServiceConstants.XWebinarSubscriberCollectionName;
         }
 
         public override string GetInQuerySingleName()
         {
-            return "webinarSubscriber";
+            return XWebinarServiceConstants.XWebinarSubscriberSingleName;
         }
     }
 }