Function negotiated_auth_proof 

pub fn negotiated_auth_proof(
    access_token: &[u8],
    direction: AuthDirection,
    role: ClientRole,
    client_nonce: &[u8; 32],
    server_nonce: &[u8; 32],
    offer: &ClientCompatibilityOffer,
    selected: &NegotiatedNodeCompatibility,
) -> Result<[u8; 32], String>