GW5, How Can I Log error messages to the Geocortex Essentials - server side ?

Hello, 

I am trying to find a way to log error messages that occur at the front-end HTML5 viewer into the server side to keep track of it. 

I could not find straightforward activities like the old XAML in GW4? Any idea?  

Best, 
YOusef 
Software Engineer | Schneider Electric