Stream.BigbytesBigbytes offers versions of each of the above formatters, which get their value from a Sodium.bigbytes value.
val secret_key : storage Fmt.tsecret_key formats a secret_key in this fashion: (Stream.secret_key AAAAAA==). If the storage value is not Sodium.Stream.secret_key_size bytes long, it will be formatted as (Stream.secret_key <size mismatch>).