feat: withdraw liquidity on burnMint

contracts/src/v0.8/ccip/pools/GHO/UpgradeableBurnMintTokenPool.sol

@@ -84,6 +84,18 @@ contract UpgradeableBurnMintTokenPool is Initializable, UpgradeableBurnMintToken
     _setRateLimitConfig(remoteChainSelector, outboundConfig, inboundConfig);
   }
 
+  /// @notice This function allows the owner to burn `amount` of the pool's token. This is
+  /// expected to be called while migrating liquidity to another pool and offboarding this
+  /// facilitator.
+  /// @dev New token pool should mint and transfer liquidity to this pool (since it does not
+  /// hold tokens any point in point, only mints/burns) which can be burnt and hence will reset
+  /// the facilitator bucket level GHO. This is needed to migrate facilitators, by offboarding
+  /// this token pool subsequently.
+  /// @param amount The amount of tokens to burn.
+  function withdrawLiquidity(uint256 amount) external onlyOwner {
+    IBurnMintERC20(address(i_token)).burn(amount);
+  }
+
   /// @inheritdoc UpgradeableBurnMintTokenPoolAbstract
   function _burn(uint256 amount) internal virtual override {
     IBurnMintERC20(address(i_token)).burn(amount);

contracts/src/v0.8/ccip/pools/GHO/diffs/UpgradeableBurnMintTokenPool_diff.md

@@ -1,9 +1,9 @@
 ```diff
 diff --git a/src/v0.8/ccip/pools/BurnMintTokenPool.sol b/src/v0.8/ccip/pools/GHO/UpgradeableBurnMintTokenPool.sol
-index 9af0f22f4c..a5cecc0430 100644
+index 9af0f22f4c..bbd4d018a5 100644
 --- a/src/v0.8/ccip/pools/BurnMintTokenPool.sol
 +++ b/src/v0.8/ccip/pools/GHO/UpgradeableBurnMintTokenPool.sol
-@@ -1,28 +1,90 @@
+@@ -1,28 +1,102 @@
  // SPDX-License-Identifier: BUSL-1.1
 -pragma solidity 0.8.19;
 +pragma solidity ^0.8.0;
@@ -106,6 +106,18 @@ index 9af0f22f4c..a5cecc0430 100644
 +    _setRateLimitConfig(remoteChainSelector, outboundConfig, inboundConfig);
 +  }
 +
++  /// @notice This function allows the owner to burn `amount` of the pool's token. This is
++  /// expected to be called while migrating liquidity to another pool and offboarding this
++  /// facilitator.
++  /// @dev New token pool should mint and transfer liquidity to this pool (since it does not
++  /// hold tokens any point in point, only mints/burns) which can be burnt and hence will reset
++  /// the facilitator bucket level GHO. This is needed to migrate facilitators, by offboarding
++  /// this token pool subsequently.
++  /// @param amount The amount of tokens to burn.
++  function withdrawLiquidity(uint256 amount) external onlyOwner {
++    IBurnMintERC20(address(i_token)).burn(amount);
++  }
++
 +  /// @inheritdoc UpgradeableBurnMintTokenPoolAbstract
    function _burn(uint256 amount) internal virtual override {
      IBurnMintERC20(address(i_token)).burn(amount);

contracts/src/v0.8/ccip/test/pools/GHO/GhoTokenPoolRemote.t.sol

@@ -398,3 +398,23 @@ contract GhoTokenPoolRemote_proxyPool is GhoTokenPoolRemoteSetup {
     assertEq(s_pool.getProxyPool(), proxyPool);
   }
 }
+
+contract GhoTokenPoolRemote_withdrawLiquidity is GhoTokenPoolRemoteSetup {
+  function testWithdrawLiquidityOnlyOwner() public {
+    vm.startPrank(STRANGER);
+    vm.expectRevert("Only callable by owner");
+    s_pool.withdrawLiquidity(13e7);
+  }
+
+  function testFuzzWithdrawLiquiditySuccess(uint256 amount) public {
+    amount = bound(amount, 1, type(uint128).max); // bound to bucket capacity
+    // prank newTokenPool.transferLiquidity
+    vm.startPrank(address(s_pool));
+    s_burnMintERC677.mint(address(s_pool), amount);
+
+    vm.startPrank(AAVE_DAO);
+    s_pool.withdrawLiquidity(amount);
+
+    assertEq(s_burnMintERC677.balanceOf(address(s_pool)), 0);
+  }
+}