Adds base model for attributes getter

src/models/answer.ts

@@ -1,10 +1,13 @@
 import { AnswerModel } from '../types/models';
 import { AnswerParameters } from '../types/parameters';
+import Model from './model';
 
-export default class Answer implements AnswerModel {
+export default class Answer extends Model implements AnswerModel {
   protected attributes: AnswerParameters;
 
   constructor() {
+    super();
+
     this.attributes = {
       question: null,
       value: null,

src/models/model.ts

@@ -0,0 +1,11 @@
+export default class Model {
+  protected attributes: object;
+
+  constructor() {
+    this.attributes = {};
+  }
+
+  public getAttributes() {
+    return this.attributes;
+  }
+}

src/models/preference.ts

@@ -1,13 +1,16 @@
 import { PreferenceModel } from '../types/models';
 import { PreferenceParameters } from '../types/parameters';
+import Model from './model';
 
 const NEXT_AVAILABLE = 1;
 const CERTAIN_DAYS = 2;
 
-export default class Preference implements PreferenceModel {
+export default class Preference extends Model implements PreferenceModel {
   protected attributes: PreferenceParameters;
 
   constructor() {
+    super();
+
     this.attributes = {
       day: null,
       end: null,