Added donor donation amount to the donor response

ref #66

src/models/entities/Donor.ts

@@ -1,4 +1,4 @@
-import { IsBoolean } from "class-validator";
+import { IsBoolean, IsInt } from "class-validator";
 import { ChildEntity, Column, OneToMany } from "typeorm";
 import { ResponseDonor } from '../responses/ResponseDonor';
 import { Donation } from './Donation';
@@ -24,6 +24,15 @@ export class Donor extends Participant {
   @OneToMany(() => Donation, donation => donation.donor, { nullable: true })
   donations: Donation[];
 
+  /**
+   * Returns the total donations of a donor based on his linked donations.
+  */
+  @IsInt()
+  public get donationAmount(): number {
+    if (!this.donations) { return 0; }
+    return this.donations.reduce((sum, current) => sum + current.amount, 0);
+  }
+
   /**
    * Turns this entity into it's response class.
    */