Implemented the interface in all responses

refr #132

src/models/responses/ResponseDonation.ts

@@ -1,11 +1,20 @@
 import { IsInt, IsNotEmpty, IsPositive } from "class-validator";
 import { Donation } from '../entities/Donation';
+import { ResponseObjectType } from '../enums/ResponseObjectType';
+import { IResponse } from './IResponse';
 import { ResponseDonor } from './ResponseDonor';
 
 /**
  * Defines the donation response.
 */
-export class ResponseDonation {
+export class ResponseDonation implements IResponse {
+
+    /**
+    * The responseType.
+    * This contains the type of class/entity this response contains.
+    */
+    responseType: ResponseObjectType = ResponseObjectType.DONATION;
+
     /**
      * The donation's id.
      */