einkaufszettel/app/adapters/application.js

import JSONAPIAdapter from '@ember-data/adapter/json-api';

export default class ApplicationAdapter extends JSONAPIAdapter {
    namespace = 'api';

  buildURL(...args) {return `${super.buildURL(...args)}.json`;}

  urlForUpdateRecord(id, modelName, snapshot) {
    return `api/${modelName}s`;
  }  
}