internal static void Sign(IInvoice invoice, Ed25519PrivateKeyParameters privateKey)
{
var ed25519Signer = new Ed25519Signer();
ed25519Signer.Init(true, privateKey);
ed25519Signer.BlockUpdate(invoice.TxBytes.ToArray(), 0, invoice.TxBytes.Length);
var signature = ed25519Signer.GenerateSignature();
ed25519Signer.Reset();
var publicKey = privateKey.GeneratePublicKey().GetEncoded();
var prefix = new ReadOnlyMemory <byte>(publicKey, 0, Math.Min(Math.Max(6, invoice.MinimumDesiredPrefixSize), publicKey.Length));
invoice.AddSignature(KeyType.Ed25519, prefix, signature);
}
