feat: simplified SafeERC20

Forked OZ's 4.8.3 version and removed unused functions:
https://github.com/OpenZeppelin/openzeppelin-contracts/blob/v4.8.3/contracts/token/ERC20/utils/SafeERC20.sol

contracts/common/SafeERC20.sol

@@ -2,55 +2,29 @@ pragma solidity ^0.8.0;
 
 import { IERC20MintableBurnable as IERC20 } from "contracts/common/IERC20MintableBurnable.sol";
 import { Address } from "openzeppelin-contracts-next/contracts/utils/Address.sol";
-//TODO: merge with lattest impl of openzeppelin
+
 /**
  * @title SafeERC20
  * @dev Wrappers around ERC20 operations that throw on failure (when the token
  * contract returns false). Tokens that return no value (and instead revert or
  * throw on failure) are also supported, non-reverting calls are assumed to be
  * successful.
- * To use this library you can add a `using SafeERC20 for ERC20;` statement to your contract,
+ * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
  * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
  */
 library SafeERC20 {
   using Address for address;
 
-  function safeTransfer(IERC20 token, address to, uint256 value) internal {
-    callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
-  }
-
   function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
-    callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
+    _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
   }
 
   function safeMint(IERC20 token, address account, uint256 amount) internal {
-    callOptionalReturn(token, abi.encodeWithSelector(token.mint.selector, account, amount));
+    _callOptionalReturn(token, abi.encodeWithSelector(token.mint.selector, account, amount));
   }
 
   function safeBurn(IERC20 token, uint256 amount) internal {
-    callOptionalReturn(token, abi.encodeWithSelector(token.burn.selector, amount));
-  }
-
-  function safeApprove(IERC20 token, address spender, uint256 value) internal {
-    // safeApprove should only be called when setting an initial allowance,
-    // or when resetting it to zero. To increase and decrease it, use
-    // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
-    // solhint-disable-next-line max-line-length
-    require(
-      (value == 0) || (token.allowance(address(this), spender) == 0),
-      "SafeERC20: approve from non-zero to non-zero allowance"
-    );
-    callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
-  }
-
-  function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
-    uint256 newAllowance = token.allowance(address(this), spender) + value;
-    callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
-  }
-
-  function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
-    uint256 newAllowance = token.allowance(address(this), spender) - value;
-    callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
+    _callOptionalReturn(token, abi.encodeWithSelector(token.burn.selector, amount));
   }
 
   /**
@@ -59,24 +33,14 @@ library SafeERC20 {
    * @param token The token targeted by the call.
    * @param data The call data (encoded using abi.encode or one of its variants).
    */
-  function callOptionalReturn(IERC20 token, bytes memory data) private {
+  function _callOptionalReturn(IERC20 token, bytes memory data) private {
     // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
-    // we're implementing it ourselves.
-
-    // A Solidity high level call has three parts:
-    //  1. The target address is checked to verify it contains contract code
-    //  2. The call itself is made, and success asserted
-    //  3. The return value is decoded, which in turn checks the size of the returned data.
-    // solhint-disable-next-line max-line-length
-    require(address(token).isContract(), "SafeERC20: call to non-contract");
-
-    // solhint-disable-next-line avoid-low-level-calls
-    (bool success, bytes memory returndata) = address(token).call(data);
-    require(success, "SafeERC20: low-level call failed");
+    // we're implementing it ourselves. We use {Address-functionCall} to perform this call, which verifies that
+    // the target address contains contract code and also asserts for success in the low-level call.
 
+    bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
     if (returndata.length > 0) {
       // Return data is optional
-      // solhint-disable-next-line max-line-length
       require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
     }
   }