message: add getters for id and type to model
diff: @@ -8,6 +8,14 @@ module.exports = class Model {
  priv.set(this, { contentType, jsonapiDoc, read, schema });
  }
  + get id() {
  + return priv.get(this).jsonapiDoc.id;
  + }
  +
  + get type() {
  + return priv.get(this).jsonapiDoc.type;
  + }
  +
  getContentType() {
  return priv.get(this).contentType;
  }
  