Restore cookie capabilities

[Kaliumhexacyanoferrat]

Try to use only extension methods, as they are basically headers.

// reading, should work for both multiple headers as well as multiple values in one header
var cookieValue = request.Header.Headers.GetCookie(...); // string or ByteString

var cookies = request.Header.Headers.GetCookies(); // allocates

// writing
response.Cookie("Key", "Value", maxAge: DateTime.UtcNow.AddDays(30)); // additional switches