Installing Boostrap 4 on ember js

I've looked around but can't find the proper way to include boostrap with ember. I don't want the ember-boostrap package since it doesn't support boostrap 4.

I'm also lost about every article outhere telling to use bower to install it but since bower is being remplaced with yarn I don't want to use a deprecated method.

I've try many times but it always fail when I'm trying to import the boostrap.js file in my ember-cli-build.js like so --> app.import('bower_components/bootstrap-sass-official/assets/javascripts/bootstrap.js'); I'm having this error

The Broccoli Plugin: [BroccoliMergeTrees: TreeMerger (vendor & appJS)] 
failed with:
Error: ENOENT: no such file or directory, open '/private/tmp/my-first-
ember-app/tmp/source_map_concat-input_base_path-
http://ift.tt/2AaCMkx
official/assets/javascripts/bootstrap.js'

Many thanks !