Ember dealing with custom API and embedded relationships

I'm trying to make ember work with a kind of custom API. The api response, for a single record, looks similar to this:

{
    id: "12345",
    name: "ObjName",
    functions: [
        "function1",
        "function2"
    ],
    participants: [
        {
            name: "participantName1",
            role: "participantRole1",
            definition: "participantDefinition1",
            features: [
                {
                    type: "feature1",
                    description: "featureDescription1"
                },
                {
                    type: "feature2",
                    description: "featureDescription2"
                }
            ]
        },
        {
            name: "participantName2",
            role: "participantRole2",
            definition: "participantDefinition2",
            features: [
                {
                    type: "feature1",
                    description: "featureDescription1"
                },
                {
                    type: "feature2",
                    description: "featureDescription2"
                }
           ]
       }
   ]
}

I'm able to retrieve the JSON and using the JSONSerializer I'm also able to map the attributes to the model:

import EmbeddedRecordsMixin from 'ember-data/serializers/embedded-records-mixin';

export
default JSONSerializer.extend(EmbeddedRecordsMixin, {

  normalizeFindRecordResponse(store, type, payload) {
    return {
      data: {
        id: payload.ac,
        type: type.modelName,
        attributes: {
          name: payload.name,
          functions: payload.functions,
          participants: payload.participants,
        }
      }
    };
  }
});

This is where I'm struggling. Since this is not a common API, I'm not sure how to make the embedded relationships accessible. In the template for this object, I have no problem to display , which displays the name attribute. But if I try to do something like this:

  
      <li></li>
  

Nothing is displayed. Has anyone experience with such customised APIs?

Thanks in advance.