contracts: create account ownership implementation

src/stamps/AccountOwnershipStamp.sol

@@ -0,0 +1,58 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.20;
+
+import "./Stamp.sol";
+
+contract AccountOwnershipStamp is Stamp {
+    string public PLATFORM;
+
+    error InvalidRecipient();
+
+    constructor(
+        address _signer,
+        string memory _platform
+    ) Stamp("Account Ownership Stamp", "AOS", "0.1.0", _signer) {
+        PLATFORM = _platform;
+    }
+
+    function mintStamp(
+        string calldata id,
+        uint256 deadline,
+        bytes calldata signature
+    ) external returns (uint256) {
+        if (msg.sender == address(0)) revert InvalidRecipient();
+
+        bytes memory encodedData = abi.encode(
+            PLATFORM,
+            id,
+            msg.sender,
+            deadline
+        );
+
+        return _mintStamp(msg.sender, encodedData, signature, deadline);
+    }
+
+    function getTypedDataHash(
+        bytes memory data
+    ) public pure override returns (bytes32) {
+        (
+            string memory platform,
+            string memory id,
+            address recipient,
+            uint256 deadline
+        ) = abi.decode(data, (string, string, address, uint256));
+
+        return
+            keccak256(
+                abi.encode(
+                    keccak256(
+                        "AccountOwnership(string platform,string id,address recipient,uint256 deadline)"
+                    ),
+                    keccak256(bytes(platform)),
+                    keccak256(bytes(id)),
+                    recipient,
+                    deadline
+                )
+            );
+    }
+}

src/stamps/Stamp.sol

@@ -29,14 +29,22 @@ abstract contract Stamp is ERC721Enumerable, EIP712 {
     error AlreadyMintedStamp(address user, uint256 stampId);
     // New custom error for invalid signature
     error InvalidSignature();
+    // New custom error for expired deadline
+    error DeadlineExpired(uint256 deadline, uint256 currentTimestamp);
 
-    // Internal minting function
+    // Modified internal minting function
     function _mintStamp(
         address to,
-        bytes calldata data,
-        bytes calldata signature
+        bytes memory data,
+        bytes calldata signature,
+        uint256 deadline
     ) internal virtual returns (uint256) {
-        if (!_verify(data, signature)) {
+        // Check if the deadline has passed
+        if (block.timestamp > deadline) {
+            revert DeadlineExpired(deadline, block.timestamp);
+        }
+
+        if (!_verifySignature(data, signature)) {
             revert InvalidSignature();
         }
 
@@ -51,8 +59,8 @@ abstract contract Stamp is ERC721Enumerable, EIP712 {
     }
 
     // Signature verification
-    function _verify(
-        bytes calldata data,
+    function _verifySignature(
+        bytes memory data,
         bytes calldata signature
     ) internal view returns (bool) {
         return