"is-active" class on all menu levels
You can achieve that by using the Menu Trail By Path module.


  Menu Trail By Path sets the active-trail on menu items according to
  the current url.
  
  For example if you are at yoursite.com/blog/category1/article1 Menu
  Items with these paths will get the active-trail class on them and
  expand accordingly.
  
  blog blog/category1 blog/category1/article1
  
  8.x-1.x branch
  
  8.x-1.x branch is completely rewritten. It should be compatible with any menu.