Function authenticate 

pub fn authenticate(
    package: &Package,
    key: &LocalSharedStatePackageKey,
    context: LocalSharedStatePackageContext,
    stream_id: [u8; 32],
    bootstrap_id: [u8; 32],
    membership_predecessor: [u8; 32],
) -> Result<(), Error>

Authenticates all domain, manifest and image bytes under the supplied key and expected context. This does not establish membership authorization.