Convert MVC5's QueryString to a List<KeyValuePair<string, StringValues>> needed by ShopifySharp's auth service.

example.cs

namespace MyNamespace
{
  public static class Extensions
  {
    public List<KeyValuePair<string, StringValues>> ToKvps(this System.Collections.Specialized.NameValueCollection qs)
    {
      Dictionary<string, string> parameters = qs.Keys.Cast<string>().ToDictionary(key => key, value => qs[value]);
      var kvps = new List<KeyValuePair<string, StringValues>>();
      
      parameters.ToList().ForEach(x =>
      {
        kvps.Add(new KeyValuePair<string, StringValues>(x.Key, new StringValues(x.Value)));
      });
      
      return kvps;
    }
  }
}