/// <summary>
/// Import pkcs8 RSA private key
/// </summary>
/// <param name="rsa"></param>
/// <param name="privateKey"></param>
/// <param name="bytesRead"></param>
/// <exception cref="ArgumentNullException"></exception>
public static void ImportPkcs8PrivateKey(this RSA rsa, ReadOnlySpan <byte> privateKey, out int bytesRead)
{
if (rsa is null)
{
throw new ArgumentNullException(nameof(rsa));
}
bytesRead = privateKey.Length;
var key = Convert.ToBase64String(privateKey.ToArray());
rsa.FromPkcs8PrivateString(key, out _);
}