Using Addons in Vaadin 8 with Spring Boot

Hi,

I am using Vaadin 8 with Spring Boot. I tried to add one addon to my project so I added the dependency and the repository to my pom.xml. But I got a problem where the addon is not compiled in widgetset. I don't have the application.gwt.xml file created anywhere since Spring boot initializer did not create that for me. And in Vaadin 7 I remember I used to have that file and add every addon in there.
So I followed the CDN way with plugin to compile the widgets it worked fine. But when I tried the NO CDN way following:
https://github.com/mstahv/spring-data-vaadin-crud/tree/without-wscdn
I got an issue regarding no webapp/VAADIN not created and the page is not loading due to missing some .js files. In Spring boot I have my theme related files defined under resources.

1. My question is how to fix the without CDN way?
2. In production what do you guys recommend CDN or NO CDN?

Thanks

I just went thru this page: 
https://vaadin.com/docs/-/part/framework/addons/addons-maven.html

I would like to implement the:

<vaadin.widgetset.mode>fetch</vaadin.widgetset.mode>

How can I do that with Spring Boot and Vaadin?