feat: make WETH an ERC20 faucet

This will let us print free WETH for manual testing & demos.

contracts/src/deployment.sol

@@ -2,8 +2,6 @@
 
 pragma solidity 0.8.18;
 
-import "openzeppelin-contracts/contracts/token/ERC20/ERC20.sol";
-
 import "./ActivePool.sol";
 import "./BoldToken.sol";
 import "./BorrowerOperations.sol";
@@ -17,6 +15,7 @@ import "./StabilityPool.sol";
 import "./TroveManager.sol";
 import "./MockInterestRouter.sol";
 import "./test/TestContracts/PriceFeedTestnet.sol";
+import {ERC20Faucet} from "./test/TestContracts/ERC20Faucet.sol";
 
 struct LiquityContracts {
     IActivePool activePool;
@@ -34,7 +33,12 @@ struct LiquityContracts {
 }
 
 function _deployAndConnectContracts() returns (LiquityContracts memory contracts) {
-    contracts.WETH = new ERC20("Wrapped ETH", "WETH");
+    contracts.WETH = new ERC20Faucet(
+        "Wrapped ETH", // _name
+        "WETH", //        _symbol
+        10 ether, //      _tapAmount
+        1 days //         _tapPeriod
+    );
 
     // TODO: optimize deployment order & constructor args & connector functions
 

contracts/src/test/TestContracts/ERC20Faucet.sol

@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: GPL-3.0
+pragma solidity 0.8.18;
+
+import "openzeppelin-contracts/contracts/token/ERC20/ERC20.sol";
+import "openzeppelin-contracts/contracts/access/Ownable.sol";
+
+contract ERC20Faucet is ERC20, Ownable {
+    uint256 public immutable tapAmount;
+    uint256 public immutable tapPeriod;
+
+    mapping(address => uint256) public lastTapped;
+
+    constructor(string memory _name, string memory _symbol, uint256 _tapAmount, uint256 _tapPeriod)
+        ERC20(_name, _symbol)
+    {
+        tapAmount = _tapAmount;
+        tapPeriod = _tapPeriod;
+    }
+
+    function mint(address _to, uint256 _amount) external onlyOwner {
+        _mint(_to, _amount);
+    }
+
+    function tapTo(address receiver) public {
+        uint256 timeNow = _requireNotRecentlyTapped(receiver);
+
+        _mint(receiver, tapAmount);
+        lastTapped[receiver] = timeNow;
+    }
+
+    function tap() external {
+        tapTo(msg.sender);
+    }
+
+    function _requireNotRecentlyTapped(address receiver) internal view returns (uint256 timeNow) {
+        timeNow = block.timestamp;
+
+        require(timeNow >= lastTapped[receiver] + tapPeriod, "ERC20Faucet: must wait before tapping again");
+    }
+}