What is the right way to upload images to server (or S3) in Ember.js?

I have application built on Ember.js (2.13). I have User model and at this moment I work on avatar upload feature. When I modify model and save it then Ember makes PATCH request to my API during it Ember serializer builds nice json-api object and I like it.

When I need to upload image to server I need to make some PUT request to my API with file data I could use jQuery ajax for this. Server will resize and crop image and save it on disk or push it to S3 bucket. But I do not like this way because this request will be created bypassing Ember's serializer and without references to model. So I need to set uploaded filename to User model and save it then I'll have redundant request to server.

I have an idea to transform file to base64 string in Ember.js app and set this string to User model and save it. In this case I'll have one request to server. Is this good way to upload file?

Please advice best practice of uploading files in Ember.js application.