fix: Support Multiple Shells (#17)

* fix: Support Multiple Shells

* CHANGEGLOG

contracts/zero-ex/contracts/src/transformers/bridges/BridgeAdapter.sol

@@ -89,7 +89,7 @@ contract BridgeAdapter is
         MixinMooniswap(addresses)
         MixinMStable(addresses)
         MixinOasis(addresses)
-        MixinShell(addresses)
+        MixinShell()
         MixinSushiswap(addresses)
         MixinUniswap(addresses)
         MixinUniswapV2(addresses)

contracts/zero-ex/contracts/src/transformers/bridges/mixins/MixinAdapterAddresses.sol

@@ -44,7 +44,6 @@ contract MixinAdapterAddresses
         address uniswapV2Router;
         address uniswapExchangeFactory;
         address mStable;
-        address shell;
         address dodoHelper;
         // Other
         address weth;

contracts/zero-ex/contracts/src/transformers/bridges/mixins/MixinShell.sol

@@ -44,15 +44,6 @@ contract MixinShell is
 {
     using LibERC20TokenV06 for IERC20TokenV06;
 
-    /// @dev Mainnet address of the `Shell` contract.
-    IShell private immutable SHELL;
-
-    constructor(AdapterAddresses memory addresses)
-        public
-    {
-        SHELL = IShell(addresses.shell);
-    }
-
     function _tradeShell(
         IERC20TokenV06 buyToken,
         uint256 sellAmount,
@@ -61,15 +52,15 @@ contract MixinShell is
         internal
         returns (uint256 boughtAmount)
     {
-        (address fromTokenAddress) = abi.decode(bridgeData, (address));
+        (address fromTokenAddress, address pool) = abi.decode(bridgeData, (address, address));
 
         // Grant the Shell contract an allowance to sell the first token.
         IERC20TokenV06(fromTokenAddress).approveIfBelow(
-            address(SHELL),
+            pool,
             sellAmount
         );
 
-        boughtAmount = SHELL.originSwap(
+        boughtAmount = IShell(pool).originSwap(
             fromTokenAddress,
             address(buyToken),
              // Sell all tokens we hold.

contracts/zero-ex/test/transformers/fill_quote_transformer_test.ts

@@ -77,7 +77,6 @@ blockchainTests.resets('FillQuoteTransformer', env => {
                 mStable: NULL_ADDRESS,
                 weth: NULL_ADDRESS,
                 shellBridge: NULL_ADDRESS,
-                shell: NULL_ADDRESS,
                 creamBridge: NULL_ADDRESS,
                 dodoBridge: NULL_ADDRESS,
                 dodoHelper: NULL_ADDRESS,