Ember-Data: Updating a model with embedded models

I’m trying to update a Discussion model with associated Tag models. I’ve created a save action that removes all the associated tags, and then adds the updated list, but the expected api calls are not made (DELETEs on tags specifically). I recently posted this question to StackOverflow, but didn’t get any traction there.

Here’s the relevant link

Was hoping someone here could provide a little direction that might get me started. If I’m missing any necessary context, please let me know!