[FEATURE] Add ERC20 setMetadata

[Conight]

bytes32 constant ERC20_METADATA_STORAGE_POSITION = keccak256("compose.erc20.metadata");

/**
 * @custom:storage-location erc8042:compose.erc20.metadata
 */
struct ERC20MetadataStorage {
    string name;
    string symbol;
    uint8 decimals;
}

function getERC20MetadataStorage() pure returns (ERC20MetadataStorage storage s) {
    bytes32 position = ERC20_METADATA_STORAGE_POSITION;
    assembly {
        s.slot := position
    }
}

function setMetadata(string memory _name, string memory _symbol, uint8 memory _decimals) {
    ERC721Storage storage s = getERC20MetadataStorage();
    s.name = _name;
    s.symbol = _symbol;
    s.decimals= _decimals;
}

I’m a bit confusing on the file structure. Should we use a full ERC20Metadata/ directory, or just an ERC20MetadataMod.sol file, or just add to exist ERC20Mod.sol contract? To stay consistent with the current setup, a dedicated folder probably makes more sense. Also, the ERC20Burn also needs better location maybe?

We may need to implement an improved directory hierarchy.

[lumoswiz]

Yeah, to me it looks like the ERC20Mod is missing the metadata storage space, however, I was unsure if this was by design. It already has the newer transfer storage implemented.

[Conight]

Yeah, to me it looks like the ERC20Mod is missing the metadata storage space, however, I was unsure if this was by design. It already has the newer transfer storage implemented.

ERC20Metadata, as an optional function, should have its own folder, similar to ERC20Permit or ERC20Bridgeable.
And i think ERC20TransferFacet should rename to old ERC20Facet.sol cause its base facet.
Currently, the dependencies are quite unclear: some are standalone modules, while others require a top-level facet.

[Conight]

I'm thinking about breaking them apart completely

├───ERC20
│   │   ERC20Facet.sol
│   │   ERC20Mod.sol
│   │
│   ├───ERC20Bridgeable
│   ├───ERC20Burn
│   ├───ERC20Metadata
│   └───ERC20Permit
├───ERC721
│   │   ERC721Facet.sol
│   │   ERC721Mod.sol
│   │
│   ├───ERC721Burn
│   └───ERC721Metadata
└───ERC721Enumerable
    │   ERC721EnumerableFacet.sol
    │   ERC721EnumerableMod.sol
    │
    ├───ERC721EnumerableBurn
    ├───ERC721EnumerableMetadata
    └───ERC721EnumerableOther

Each folder will contain core like ERC20Facet.sol/ERC20Mod.sol and optional facets. Any components without direct dependencies should reside on the same level.
I'd love to hear feedback on this.

[Conight]

#261

[mudgen]

@Conight @lumoswiz I am looking at this, thank you.

[mudgen]

I have reorganized ERC20 and ERC721 code.