Problem Description

I'm working with an existing open source auction Rust program for Solana. Currently, Sol is held in escrow and the user manually has to withdraw their Sol if they get outbid. This is not good UX, so I'd like you to modify the open auction (aka English auction) bid function so that if there is a previous bid, the previous bidder gets refunded in the same transaction as the next bid.

This is the program I'm starting from, I expect most of your changes will be in the make_open_bid function in lib.rs:
https://github.com/udbhav1/solana-auctionhouse

Acceptance Criteria

The program needs to compile and pass tests, ideally you would write a few new tests to demonstrate that the refunding functionality works.