Add documentation for ERC-7702 delegation (#105)

Author: ernestognw

contracts/mocks/docs/account/MyAccountERC7702.sol

@@ -0,0 +1,20 @@
+// contracts/MyAccountERC7702.sol
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.20;
+
+import {Account} from "../../../account/Account.sol";
+import {ERC721Holder} from "@openzeppelin/contracts/token/ERC721/utils/ERC721Holder.sol";
+import {ERC1155Holder} from "@openzeppelin/contracts/token/ERC1155/utils/ERC1155Holder.sol";
+import {ERC7821} from "../../../account/extensions/ERC7821.sol";
+import {SignerERC7702} from "../../../utils/cryptography/SignerERC7702.sol";
+
+contract MyAccountERC7702 is Account, SignerERC7702, ERC7821, ERC721Holder, ERC1155Holder {
+    /// @dev Allows the entry point as an authorized executor.
+    function _erc7821AuthorizedExecutor(
+        address caller,
+        bytes32 mode,
+        bytes calldata executionData
+    ) internal view virtual override returns (bool) {
+        return caller == address(entryPoint()) || super._erc7821AuthorizedExecutor(caller, mode, executionData);
+    }
+}

contracts/utils/README.adoc

@@ -23,6 +23,8 @@ Miscellaneous contracts and libraries containing utility functions you can use t
 
 {{SignerP256}}
 
+{{SignerERC7702}}
+
 {{SignerRSA}}
 
 == Libraries

docs/modules/ROOT/pages/account-abstraction.adoc

@@ -180,3 +180,20 @@ These rules outline the requirements for operations to be processed by the canon
 Accounts can access its own storage during the validation phase, they might easily violate ERC-7562 storage access rules in undirect ways. For example, most accounts access their public keys from storage when validating a signature, limiting the ability of having accounts that validate operations for other accounts (e.g. via ERC-1271)
 
 TIP: Although any Account that breaks such rules may still be processed by a private bundler, developers should keep in mind the centralization tradeoffs of relying on private infrastructure instead of _permissionless_ execution.
+
+=== EIP-7702 Delegation
+
+EIP-7702 enables EOAs to temporarily delegate their execution capabilities to smart contracts. This is particularly useful for:
+
+* Batching multiple operations in a single transaction
+* Sponsoring transactions for other users
+* Implementing privilege de-escalation (e.g., sub-keys with limited permissions)
+
+xref:api:utils.adoc#SignerERC7702[`SignerERC7702`] helps implement EIP-7702 delegation in smart contract accounts by validating signatures using the EOA's address (i.e., `address(this)`).
+
+[source,solidity]
+----
+include::api:example$account/MyAccountERC7702.sol[]
+----
+
+TIP: Users can delegate to an instance of xref:api:account.adoc#ERC7821[`ERC7821`] for a minimal batch executor that does not use ERC-4337 related code.