A sequences of unique nonces.
NonceSequence must never return the same
Nonce twice from
A simple counter is a reasonable (but probably not ideal)
Copy since cloning would allow duplication
of the sequence.
fn advance(&mut self) -> Result<Nonce, Unspecified>
Returns the next nonce in the sequence.
This may fail if "too many" nonces have been requested, where how many
is too many is up to the implementation of
implementation may that enforce a maximum number of records are
sent/received under a key this way. Once
advance() fails, it must
fail for all subsequent calls.