Ember.js - Mapping legacy JSON response to data model

My legacy server JSON response looks like this:

{ "foo": { … }, "bars": ["a", "b", "c", …] }

How can I map this into an Ember Data Model by extending a RESTAdapter?

My best attempt so far is the following:

app/models/rule-lookup.js:

import DS from 'ember-data';
export default DS.Model.extend({
  foo: DS.attr(),
  bars: DS.attr(),
});


app/models/foo.js:

import DS from 'ember-data';
export default DS.Model.extend({
  name: DS.attr('string'),
  description: DS.attr('string'),
});

When the user makes a choice in a select, in the controller I fetch the model with:

this.store.findRecord('rule-lookup', id);

In the adapter (inside application.js) I have put the following statements:

import DS from 'ember-data';
export default DS.RESTAdapter.extend({
  urlForFindRecord(id, modelName, snapshot) {
    switch (modelName) {
      case 'rule-lookup': {
        return `api/keys/${id}/rules/0/200`;
      }
    }
  },
});

But the error from findRecord is:

WARNING: Encountered "bars" in payload, but no model was found for model name "bar" (resolved model name using panel@serializer:rest:.modelNameFromPayloadKey("bars"))`
TypeError: Cannot read property '_internalModel' of undefined