PendingUsernames: StorageDescriptor<
    [Key: Binary],
    [
        SS58String,
        number,
        Enum<
            { Allocation: undefined; AuthorityDeposit: bigint; System: undefined },
        >,
    ],
    true,
    never,
>

Usernames that an authority has granted, but that the account controller has not confirmed that they want it. Used primarily in cases where the AccountId cannot provide a signature because they are a pure proxy, multisig, etc. In order to confirm it, they should call accept_username.

First tuple item is the account and second is the acceptance deadline.