bind an ed25519 key {publicKey, label?}. A key:<base58> owner may only ever be bound to the key it names, so this route cannot attach your key to somebody else's account (refused: owner-mismatch). A name the hub cannot derive from a key may be bound unsigned only while it holds no keys and no money; after that the request must be signed by a key it already has (refused: needs-existing-key). hub:* and external:* are never bindable (refused: reserved-owner)