Feat/mtoken min balance

[kostyamospan]

No description provided.

[gemini-code-assist]

Code Review

This pull request introduces a new minimum balance check feature for mTokens, implementing mTokenMinBalance and mTokenPermissionedMinBalance along with corresponding tests, deployment scripts, and configuration updates. The review feedback highlights a high-severity issue where hardcoding 1 ether as the minimum balance assumes 18 decimals, which would break usability for tokens with fewer decimals (such as 6 or 8 decimals). Additionally, a minor copy-paste typo was identified in the docstring of _afterTokenTransfer in mTokenPermissionedMinBalance.sol.

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[gemini-code-assist]

Hardcoding "1 ether" (which is "10**18") as the minimum balance assumes that all tokens using this contract will have 18 decimals and require exactly a 1-token minimum balance. If a token has fewer decimals (e.g., 6 decimals for USDC-pegged tokens or 8 decimals for BTC-pegged tokens), "1 ether" translates to an extremely large minimum balance (e.g., "10^12" or "10^10" tokens), making the token practically unusable.

To support tokens with different decimals and allow customization of the minimum balance, consider defining a virtual function "_minBalance()" that defaults to "10 ** decimals()" (or a customizable value) and can be overridden by specific token implementations.

    function _validateMinBalance(address user) private view {
        uint256 balance = balanceOf(user);
        require(
            balance == 0 || balance >= _minBalance(),
            "MTMB: min balance not met"
        );
    }

    /**
     * @dev returns the minimum balance required for non-exempt users
     */
    function _minBalance() internal view virtual returns (uint256) {
        return 10 ** decimals();
    }

[gemini-code-assist]

The docstring/comment for "_afterTokenTransfer" incorrectly states that it overrides "_beforeTokenTransfer". This is a copy-paste typo from the function above it.

    /**
     * @dev overrides _afterTokenTransfer function to call the parent hooks
     */
    function _afterTokenTransfer(