feat: implement invoice processing and discount management

src/modules/discounts/entities/discount.entity.ts

@@ -1,10 +1,11 @@
-import { Column, DeleteDateColumn, Entity, OneToMany } from "typeorm";
+import { Column, DeleteDateColumn, Entity, ManyToOne, OneToMany } from "typeorm";
 
 import { UsageDiscount } from "./usage-discount.entity";
 import { BaseEntity } from "../../../common/entities/base.entity";
 import { DecimalTransformer } from "../../../common/transformers/decimal.transformer";
 import { Invoice } from "../../invoices/entities/invoice.entity";
 import { SubscriptionPlan } from "../../subscriptions/entities/subscription.entity";
+import { User } from "../../users/entities/user.entity";
 import { DiscountApplicationType } from "../enums/discount-application-type.enum";
 import { DiscountType } from "../enums/discount-type.enum";
 
@@ -40,7 +41,9 @@ export class Discount extends BaseEntity {
   @DeleteDateColumn({ nullable: true })
   deletedAt?: Date;
 
-  // Relations
+  @ManyToOne(() => User, (user) => user.discounts, { nullable: true })
+  user?: User | null;
+
   @OneToMany(() => UsageDiscount, (usageDiscount) => usageDiscount.discount)
   usages: UsageDiscount[];