add versioning to contracts

contracts/RewardRatePool.sol

@@ -12,6 +12,8 @@ import "@openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol";
 contract RewardRatePool is Initializable, Ownable2StepUpgradeable {
     using SafeERC20 for IERC20;
 
+    uint256 public constant VERSION = 1;
+
     // solhint-disable-next-line var-name-mixedcase
     IERC20 public SESH;
 

contracts/SESH.sol

@@ -12,6 +12,8 @@ import "./libraries/Shared.sol";
  * @notice The SESH utility token with Arbitrum Custom Gateway support
  */
 contract SESH is ICustomToken, ERC20, ERC20Permit, Shared {
+    uint256 public constant VERSION = 1;
+
     address public immutable gateway;
     address public immutable router;
     bool private shouldRegisterGateway;

contracts/SESHL2.sol

@@ -10,6 +10,9 @@ import "./libraries/arbitrum-bridge/IArbToken.sol";
  * @notice L2 representation of the SESH token, bridged from L1
  */
 contract SESHL2 is Initializable, ERC20Upgradeable, IArbToken {
+
+    uint256 public constant VERSION = 1;
+
     address public l2Gateway;
     address public l1Address;
 

contracts/ServiceNodeContributionFactory.sol

@@ -8,6 +8,9 @@ import "@openzeppelin/contracts-upgradeable/access/Ownable2StepUpgradeable.sol";
 import "@openzeppelin/contracts-upgradeable/utils/PausableUpgradeable.sol";
 
 contract ServiceNodeContributionFactory is Initializable, Ownable2StepUpgradeable, PausableUpgradeable, IServiceNodeContributionFactory {
+
+    uint256 public constant VERSION = 1;
+
     IServiceNodeRewards public stakingRewardsContract;
 
     /// Tracks the contribution contracts that have been deployed from this

contracts/ServiceNodeRewards.sol

@@ -14,6 +14,9 @@ import "@openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol";
 /// @title Service Node Rewards Contract
 /// @notice This contract manages the rewards and public keys for service nodes.
 contract ServiceNodeRewards is Initializable, Ownable2StepUpgradeable, PausableUpgradeable, IServiceNodeRewards {
+
+    uint256 public constant VERSION = 1;
+
     using SafeERC20 for IERC20;
 
     bool public isStarted;