Function sign_request 

pub fn sign_request<S: Signer>(
    request: &CanonicalRequest<'_>,
    integrity_token: &str,
    signer: &S,
) -> Result<SignedHeaders, SignError<S::Error>>

Signs request now, with a fresh nonce.

Every attempt, including a retry or a reconnect, must be signed again: the nonce and created are what distinguish it.

Errors

Returns a SignError when no nonce can be generated or the signer fails.