Upload Old Invoices

var options = new RestClientOptions("https://apitest.nilvera.com")
{
  MaxTimeout = -1,
};
var client = new RestClient(options);
var request = new RestRequest("/earchive/Old", Method.Post);
request.AddHeader("Authorization", "Bearer <API KEY>");
request.AlwaysMultipartFormData = true;
request.AddFile("file", "/path/to/file");
RestResponse response = await client.ExecuteAsync(request);
Console.WriteLine(response.Content);