chore: add discount logic to apply to the plan price and ...

src/modules/invoices/entities/invoice.entity.ts

@@ -20,6 +20,9 @@ export class Invoice extends BaseEntity {
   @Column({ type: "decimal", precision: 16, scale: 2, nullable: false, transformer: new DecimalTransformer() })
   totalPrice: Decimal;
 
+  @Column({ type: "decimal", precision: 16, scale: 2, nullable: true, transformer: new DecimalTransformer() })
+  originalPrice?: Decimal;
+
   @Column({ type: "enum", enum: InvoiceStatus, default: InvoiceStatus.PENDING })
   status: InvoiceStatus;
 
@@ -40,8 +43,8 @@ export class Invoice extends BaseEntity {
   @OneToMany(() => InvoiceItem, (invoiceItem) => invoiceItem.invoice, { cascade: true })
   items: InvoiceItem[];
 
-  @ManyToOne(() => Discount, { nullable: true, onDelete: "SET NULL" })
-  discount: Discount;
+  @ManyToOne(() => Discount, (discount) => discount.invoices, { nullable: true, onDelete: "RESTRICT" })
+  discount?: Discount;
 
   get isOverdue(): boolean {
     return this.status === InvoiceStatus.PENDING && new Date() > this.dueDate;