// Define a custom error

error FairFund__VaultLimitExceeded(address user, uint256 maxAllowed);

State variables
uint256 public constant MAX_VAULTS_PER_ADDRESS = 5;
mapping(address => uint256) private s_vaultsCreated;

function deployFundingVault(
    address _fundingToken,
    address _votingToken,
    uint256 _minRequestableAmount,
    uint256 _maxRequestableAmount,
    uint256 _tallyDate
) external returns (address) {
    // Check if the user has reached their vault creation limit
    if (s_vaultsCreated[msg.sender] >= MAX_VAULTS_PER_ADDRESS) {
        revert FairFund__VaultLimitExceeded(msg.sender, MAX_VAULTS_PER_ADDRESS);
    }

    // Increment the vault count for the user
    s_vaultsCreated[msg.sender]++;

    // Rest of the function logic...
}