Issue K: Unsafe ERC20 Token Transfer

[daveroga]

Fix issue #133

Location

/nightfall-deployer/contracts/Shield.sol

Synopsis

ERC20 tokens transfer and transferFrom are unsafe methods for token transfers that do not adhere to the IERC20 standard of reverting in the case of failure. In some cases, these methods may cause tokens to be locked in the contract.

Impact

User funds may potentially get locked in the contract.

Remediation

We recommend the use of the standard safe transfer wrapper by OpenZeppelin.

Done

• Use of SafeERC20Upgradeable from OpenZeppelin as it's compatible with our upgradeable contracts.
• Replaced all transfers in the contract with safeTransfer and safeTransferFrom.

Refactor

• Added IERC721 and IERC1155 in order to follow also OpenZeppelin recommendations.
• Removed unused ERCInterface.sol contract.
• Removed unused ERCStub.sol, ERC721_2Mock.sol and ERC1155_2Mock.sol mocks contracts.
• Mocks in mocks folder in contracts in nightfall-developer.