Add IERC721MultiMetadata extension

contracts/token/ERC721/README.adoc

@@ -62,6 +62,8 @@ NOTE: This core set of contracts is designed to be unopinionated, allowing devel
 
 {{ERC721Wrapper}}
 
+{{IERC721MultiMetadata}}
+
 == Utilities
 
 {{ERC721Holder}}

contracts/token/ERC721/extensions/IERC721MultiMetadata.sol

@@ -0,0 +1,58 @@
+// SPDX-License-Identifier: MIT
+// OpenZeppelin Contracts v4.4.1 (token/ERC721/extensions/IERC721Metadata.sol)
+
+pragma solidity ^0.8.19;
+
+/**
+ * @title IERC721MultiMetadata (EIP-7160) optional EIP-721 multi-metadata extension
+ * @author 0xG
+ * @author mpeyfuss
+ * @dev See https://eips.ethereum.org/EIPS/eip-7160 and https://eips.ethereum.org/EIPS/eip-721
+ *      Note: the ERC-165 identifier for this interface is 0x06e1bc5b.
+ */
+interface IERC721MultiMetadata {
+    /**
+     * @dev This event emits when a token uri is pinned and is useful for indexing purposes.
+     */
+    event TokenUriPinned(uint256 indexed tokenId, uint256 indexed index, address indexed sender);
+
+    /**
+     * @dev This event emits when a token uri is unpinned and is useful for indexing purposes.
+     */
+    event TokenUriUnpinned(uint256 indexed tokenId, address indexed sender);
+
+    /**
+     * @notice Get all token uris associated with a particular token.
+     * @dev If a token uri is pinned, the index returned should be the index in the string array.
+     *
+     * @param tokenId The identifier for the NFT.
+     * @return index An unisgned integer that specifies which uri is pinned for a token (or the default uri if unpinned).
+     * @return uris A string array of all uris associated with a token.
+     */
+    function tokenURIs(uint256 tokenId) external view returns (uint256 index, string[] memory uris);
+
+    /**
+     * @notice Pin a specific token uri for a particular token.
+     *
+     * @param tokenId The identifier of the NFT.
+     * @param index The index in the string array returned from the `tokenURIs` function that should be pinned for the token.
+     */
+    function pinTokenURI(uint256 tokenId, uint256 index) external;
+
+    /**
+     * @notice Unpin metadata for a particular token.
+     * @dev This should reset the token to the default uri.
+     *
+     * @param tokenId The identifier of the NFT.
+     */
+    function unpinTokenURI(uint256 tokenId) external;
+
+    /**
+     * @notice Check on-chain if a token id has a pinned uri or not.
+     * @dev Useful for on-chain mechanics.
+     *
+     * @param tokenId The identifier of the NFT.
+     * @return pinned A bool specifying if a token has metadata pinned or not.
+     */
+    function hasPinnedTokenURI(uint256 tokenId) external view returns (bool pinned);
+}