Macro domain_separator 

macro_rules! domain_separator {
    ($protocol_fmt:literal $(, $protocol_arg:expr)* ; $session_fmt:literal $(, $session_arg:expr)* $(,)?) => { ... };
    ($fmt:literal $(, $arg:expr)* $(,)?) => { ... };
}

Build a DomainSeparator from a protocol identifier string.

Chain .session(..) or .without_session() before .instance(..).

let domsep = spongefish::domain_separator!("spongefish")
    .session(spongefish::session!("DomainSeparator"))
    .instance(b"trivial");
let _prover = domsep.std_prover();