1. create migration field service_charge in bookings. (nullable, default null, double)
2. create migration field adjustment in invoices. (nullable, default null, double)
3. save service charge on confirm
4. pass service from backend
5. display in frontend.
6. When RMB value match auto adjustment.
7. Vue validation before post and edit.
8. post and edit invoice needs to have adjustment. validate.
9. change pdf documents.
