feat(cashier): add ref key as refrence id key for the item from the emr or etc

src/entity/cashier/cashier_item.ts

@@ -108,13 +108,16 @@ export class CashierItem {
         scale: 2
     })
     balance_due: number;
-    
+
     @Column({ nullable: true })
     status: BillingItemStatus;
 
     @Column({ nullable: true, length: 256 })
     category: string;
 
+    @Column({ nullable: true, length: 256 })
+    refKey: string;
+
     @Column()
     @CreateDateColumn()
     created_at: Date;