gistfile1.txt

DS.RESTAdapter.map('App.Database', {
  primaryKey: 'name'
  collections: { embedded: 'load' }

});

DS.RESTAdapter.map('App.Collection', {
  primaryKey: 'name'
});

App.store = DS.Store.create({
    revision:11,
    adapter:DS.RESTAdapter.create({ namespace: 'api', bulkCommit:false })
});

App.Database = DS.Model.extend({
    name:DS.attr('string'),
    collections: DS.hasMany('App.Collection')
});

App.Collection = DS.Model.extend({
    name:DS.attr('string')
});

response

{
    "databases": [
        {
            "name": "fred",
            "collections": [
                {
                    "name": "test collection"
                }
            ]
        }
    ]
}