maxDeposit doesn't comply with ERC-4626

Summary

maxDeposit doesn't comply with ERC-4626 since depositing the returned amount can cause reverts

Vulnerability Detail

The contract's maxDeposit function doesn't comply with ERC-4626 which is a mentioned requirement. According to the specification, MUST return the maximum amount of assets deposit would allow to be deposited for receiver and not cause a revert .... The deposit function will revert in case the deposit is a lossy deposit ie. totalPreciseAsset function returns less than the totalDebt after the deposit. It is possible for this to occur due to rounding inside the preview redeem function of the yieldVault in the absence / depletion of yield buffer

POC

Add the following test inside pt-v5-vault/test/unit/PrizeVault/PrizeVault.t.sol

    function testHash_MaxDepositRevertLossy() public {
        PrizeVault testVault=  new PrizeVault(
            "PoolTogether aEthDAI Prize Token (PTaEthDAI)",
            "PTaEthDAI",
            yieldVault,
            PrizePool(address(prizePool)),
            claimer,
            address(this),
            YIELD_FEE_PERCENTAGE,
            0,
            address(this)
        );

        underlyingAsset.mint(address(yieldVault),100e18);
        YieldVault(address(yieldVault)).mint(address(100),99e18); // 99 shares , 100 assets

        uint maxDepositReturned = testVault.maxDeposit(address(this));

        uint amount_ = 99e18;
        underlyingAsset.mint(address(this),amount_);
        underlyingAsset.approve(address(testVault),amount_);

        assert(maxDepositReturned > amount_);

        vm.expectRevert();
        testVault.deposit(amount_,address(this));

    }

Impact

Failure to comply with the specification which is a mentioned necessity

Code Snippet

https://github.com/sherlock-audit/2024-05-pooltogether/blob/1aa1b8c028b659585e4c7a6b9b652fb075f86db3/pt-v5-vault/src/PrizeVault.sol#L991-L992

Tool used

Manual Review

Recommendation

Consider the yieldBuffer balance too inside the maxDeposit function