add VERSION (constant) to SuperToken and ISuperToken (#2137)

Author: d10r

packages/ethereum-contracts/CHANGELOG.md

@@ -8,6 +8,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 ### Added
 
 - `SuperToken`: the contract admin can enable/disable a _Yield Backend_ in order to generate a yield on the underlying asset.
+- `SuperToken`: added `VERSION()` which returns the version string of the logic contract set for the SuperToken, and inline CHANGELOG.
 
 ### Changed
 

packages/ethereum-contracts/contracts/interfaces/superfluid/ISuperToken.sol

@@ -34,6 +34,11 @@ interface ISuperToken is ISuperfluidToken, IERC20Metadata, IERC777, IERC20Permit
     error SUPER_TOKEN_PERMIT_EXPIRED_SIGNATURE(uint256 deadline);            // 0x6e72b90f
     error SUPER_TOKEN_PERMIT_INVALID_SIGNER(address signer, address owner);  // 0xb6422105
 
+    /**
+     * @dev Return the version of the SuperToken logic
+     */
+    function VERSION() external view returns (string memory);
+
     /**
      * @dev Initialize the contract
      */

packages/ethereum-contracts/contracts/superfluid/SuperToken.sol

@@ -30,6 +30,11 @@ interface IPoolMemberNFT {}
  * @title Superfluid's super token implementation
  *
  * @author Superfluid
+ *
+ * CHANGELOG:
+ * [1.0.0]
+ * Added:
+ * - support for an optional yield backend
  */
 contract SuperToken is
     UUPSProxiable,
@@ -40,6 +45,8 @@ contract SuperToken is
     using ERC777Helper for ERC777Helper.Operators;
     using SafeERC20 for IERC20;
 
+    string public constant override VERSION = "1.0.0";
+
     // See: https://eips.ethereum.org/EIPS/eip-1967#admin-address
     bytes32 constant private _ADMIN_SLOT = 0xb53127684a568b3173ae13b9f8a6016e243e63b6e8ee1178d6a717850b5d6103;