feat: do not cache chain id for permit

contracts/token-implementations/ERC20Permit.sol

@@ -22,7 +22,7 @@ abstract contract ERC20Permit is IERC20, IERC20Permit, ERC20 {
      * @dev Represents hash of the EIP-712 Domain Separator.
      */
     // solhint-disable-next-line var-name-mixedcase
-    bytes32 public DOMAIN_SEPARATOR;
+    bytes32 public nameHash;
 
     string private constant EIP191_PREFIX_FOR_EIP712_STRUCTURED_DATA = '\x19\x01';
 
@@ -38,13 +38,20 @@ abstract contract ERC20Permit is IERC20, IERC20Permit, ERC20 {
     mapping(address => uint256) public nonces;
 
     /**
-     * @notice Internal function to set the domain type signature hash
+     * @notice Internal function to set the token name hash
      * @param name The token name
      */
-    function _setDomainTypeSignatureHash(string memory name) internal {
-        DOMAIN_SEPARATOR = keccak256(
-            abi.encode(DOMAIN_TYPE_SIGNATURE_HASH, keccak256(bytes(name)), keccak256(bytes('1')), block.chainid, address(this))
-        );
+    function _setNameHash(string memory name) internal {
+        nameHash = keccak256(bytes(name));
+    }
+
+    /**
+     * @notice Calculates the DOMAIN_SEPARATOR.
+     * @dev This is not cached because chainid can change on chain forks.
+     */
+    // solhint-disable-next-line func-name-mixedcase
+    function DOMAIN_SEPARATOR() public view returns (bytes32 domainSeparator) {
+        domainSeparator = keccak256(abi.encode(DOMAIN_TYPE_SIGNATURE_HASH, nameHash, keccak256(bytes('1')), block.chainid, address(this)));
     }
 
     /**
@@ -69,7 +76,7 @@ abstract contract ERC20Permit is IERC20, IERC20Permit, ERC20 {
         bytes32 digest = keccak256(
             abi.encodePacked(
                 EIP191_PREFIX_FOR_EIP712_STRUCTURED_DATA,
-                DOMAIN_SEPARATOR,
+                DOMAIN_SEPARATOR(),
                 keccak256(abi.encode(PERMIT_SIGNATURE_HASH, issuer, spender, value, nonces[issuer]++, deadline))
             )
         );

contracts/token-implementations/StandardizedToken.sol

@@ -68,7 +68,7 @@ contract StandardizedToken is IERC20BurnableMintable, InterchainToken, ERC20Perm
             name = tokenName;
 
             _setDistributor(distributor_);
-            _setDomainTypeSignatureHash(tokenName);
+            _setNameHash(tokenName);
         }
         {
             uint256 mintAmount;