Conform to and respect GDPR middleware

[rschindhelm]

Currently the tag helper disrespects the GDPR middleware by setting the language cookie via JavaScript. The cookie should be set via Response.Cookies.Append instead in order to get processed by the middleware.

Also, we should mark the cookie as essential to ensure it can be set even if the user hasn't given his consensus yet.

This change will ultimately result in the same behavior as if the cookie was set in JavaScript, but the GDPR policies might change in future, so it's presumably better to stay on the safe side.

To extend the Localization.StarterWeb example:

Response.Cookies.Append(
    CookieRequestCultureProvider.DefaultCookieName,
    CookieRequestCultureProvider.MakeCookieValue(new RequestCulture(culture)),
    new CookieOptions {
        Expires = DateTimeOffset.UtcNow.AddYears(1),
        IsEssential = true // mark language cookie as essential
    }
);

[hishamco]

Thanks René for filing this issue, I will make a PR for it, and if you like to push a PR you are welcome

thanks again ..