add way of removing a goal (#88)

closes #66

Reviewed-on: #88

frontend/allowance-planner-v2/src/app/services/allowance.service.ts

@@ -26,4 +26,8 @@ export class AllowanceService {
     updateAllowance(allowance: Partial<Allowance>, allowanceId: number, userId: number) {
         this.http.put(`${this.url}/user/${userId}/allowance/${allowanceId}`, allowance).subscribe();
     }
+
+    deleteAllowance(allowanceId: number, userId: number) {
+        this.http.delete(`${this.url}/user/${userId}/allowance/${allowanceId}`).subscribe();
+    }
 }