Rails and ember. How to handle tags?

Let’s say I have a model with tags (acts_as_taggable gem or custom code of mine).

How can I handle tags in my ember app model?

How can I change tags from ember using serialization with Rails?

If I get from server tags: [1,2] how can I add then 3? With saving tags: [1,2,3] but maybe in the meantime the 2 is missing on database so I need maybe something to add/remove a tag?