Introduce Full Native ETH Support for Auctions Including Bidding, Withdrawals, and Final Settlement

[aniket866]

Issue:
All auction contracts assume biddingToken is an ERC20 and rely exclusively on IERC20 / SafeERC20 for value transfers.
There is no support for native ETH (or the chain’s native currency), and token addresses are assumed to always be contracts.

Why It’s Critical:
Users commonly want to bid using native ETH rather than wrapped tokens (e.g., WETH).
The current design prevents ETH-based auctions and incorrectly treats address(0) as an invalid token.

Affected Areas

Files:

• Auction.sol
• AllPayAuction.sol
• EnglishAuction.sol
• VickreyAuction.sol
• LinearReverseDutchAuction.sol
• ExponentialReverseDutchAuction.sol

Repeated Assumption (example):

receiveERC20(auction.biddingToken, msg.sender, bidAmount);

Required Refactor;

Fix Overview:

• If the token address is address(0), interpret it as native ETH, not an ERC20 token.

Key Changes Required:

• Make createAuction, bid, and commitBid functions payable
• Update receiveERC20 and sendERC20 helpers to branch on token type

Example Direction:

if (token == address(0)) {
    require(msg.value == amount, "Invalid ETH value");
} else {
    IERC20(token).safeTransferFrom(from, address(this), amount);
}

if (token == address(0)) {
    (bool ok, ) = to.call{ value: amount }("");
    require(ok, "ETH transfer failed");
} else {
    IERC20(token).safeTransfer(to, amount);
}

Impact of Fix

• Allows users to bid using native ETH (no WETH needed)

• Makes bidding easier and more familiar for users

• Handles ETH and tokens in one shared transfer flow

• Affects all bid, withdraw, and claim logic across auctions

@kaneki003 What's your view on this , feel free to assign