I am developing a custom payment gateway. It uses OrderIncrementID to identify which Order was the payment made for. I have every functionality running after the Order has been placed, i.e. after checkout, except one in the checkout page itself.
In the checkout page, Order was not created, getting an OrderIncrementID seems very difficult. We have to overwrite the order creation in the checkout such that it will be created after the payment method selection which sounds very complicated and dangerous to overwrite the flow. An alternative is to use QuoteID, but the tradeoff is that I have to implement a convertion from QuoteID to OrderIncrementID.
What can I do in this case to get an OrderIncrementID in the checkout page? especially after the payment method selection
Thanks for @AmitBera answer, I will now emphasis that consistency and integrity on overlapping request is very important in this payment system. User A load the checkout page first, followed by user B. But User B complete the checkout first, followed by User A. The correct payment for correct users should be made.