Merge pull request #1265 from OneSignal/user_model/fix_json_representation

[User model] Fix PushSubscriptionChanged state json representation

Author: emawby

iOS_SDK/OneSignalSDK/OneSignalUser/Source/OSSubscriptionModel.swift

@@ -82,7 +82,7 @@ public class OSPushSubscriptionChangedState: NSObject {
     }
 
     @objc public func jsonRepresentation() -> NSDictionary {
-        return ["from": previous.jsonRepresentation(), "to": current.jsonRepresentation()]
+        return ["previous": previous.jsonRepresentation(), "current": current.jsonRepresentation()]
     }
 }