Function extend_external_storage_layout 

fn extend_external_storage_layout(
    compiler: &mut Compiler,
    path: &Path,
    name: &str,
    layout: StorageLayout,
    address: Address,
) -> StorageLayout

Appends the ERC-7201 namespaces of contract name in source path to its solc layout.

Namespaces only add decoding coverage, so on failure the solc layout is returned unchanged.