application.js

import DS from "ember-data";
import Ember from "ember";
import ENV from "frontent/config/environment";

function formatAttributeName(attr) {
  if (ENV['ember-cli-mirage'].enabled) {
    return Ember.String.camelize(attr);
  } else {
    return Ember.String.decamelize(attr);
  }
}

export default DS.JSONAPISerializer.extend({
  keyForAttribute: function(attr) {
    return formatAttributeName(attr);
  }
});