Feature/add prefix to coupon codes (#1562)

* Add prefix

* Update changelog

apps/client/src/app/components/admin-overview/admin-overview.component.ts

@@ -4,6 +4,7 @@ import { CacheService } from '@ghostfolio/client/services/cache.service';
 import { DataService } from '@ghostfolio/client/services/data.service';
 import { UserService } from '@ghostfolio/client/services/user/user.service';
 import {
+  ghostfolioPrefix,
   PROPERTY_COUPONS,
   PROPERTY_CURRENCIES,
   PROPERTY_IS_READ_ONLY_MODE,
@@ -97,7 +98,10 @@ export class AdminOverviewComponent implements OnDestroy, OnInit {
   public onAddCoupon() {
     const coupons = [
       ...this.coupons,
-      { code: this.generateCouponCode(16), duration: this.couponDuration }
+      {
+        code: `${ghostfolioPrefix}${this.generateCouponCode(14)}`,
+        duration: this.couponDuration
+      }
     ];
     this.putAdminSetting({ key: PROPERTY_COUPONS, value: coupons });
   }