"str is undefined" on findRecord

I have a problem with model and serializer. I've looked at the documentation and can't find a solution. My app is connected to a django rest api.

Django response:

{
    "id": 1,
    "url": "http://localhost:8000/users/1/",
    "username": "username",
    "email": "xxx@email.com",
    "is_staff": true
}

The model:

export default DS.Model.extend({
    url : DS.attr('string'),
    username : DS.attr('string'),
    email : DS.attr('string'),
});

I've modified the response with a serializer to include "data":

export default DS.JSONAPISerializer.extend({
    primaryKey: 'id',
    normalizeFindRecordResponse(store, type, payload, id) {
        console.log('payload',payload)
        return {
            data: {
                'id': id,
                'url': payload.url,
                'username': payload.username,
                'email': payload.email,
            }
        } ; 
    }
});

The route:

export default Ember.Route.extend({
    model() {
        return this.store.findRecord('users', 1);
    }
});

Another version of the route same error:

export default Ember.Route.extend({
    model() {
        this.store.findRecord('users', '1').then(function(user){
            console.log('user', user);
        }).catch(function(e){
            console.log('e', e);
        });
    }    
});

Finally Ember inspector has the model but all values as undefined and "str is undefined" on console.

Image of ember inspector

1.normalizeFindRecordResponse is not returning valid JSONAPI format, The below is the valid format,

{
  "data": {
    "type": "articles",
    "id": "1",
    "attributes": {
      // ... this article's attributes
    }        
  }
}

As you can see, you are missing type, attributes key.

2.Your model file name should be user.js in singular.
3.this.store.findRecord('users', 1) - here you need to use singluar form of the model so this.store.findRecord('user', 1)
4.In your another attempt you are missing the return statement in model hook.