Search requests need to correctly encode offset for date values

[kceiw]

Test version 0.36.0

The repro snippet

            var endDate = new DateTimeOffset(2012, 12, 20, 16, 0, 0, TimeSpan.FromMinutes(8 * 60)); // offset +08:00
            var startDate = endDate.AddDays(-30);
            var request = new SearchRepositoriesRequest()
            {
                Updated = DateRange.Between(startDate, endDate)
            };
            var githubClient = new GitHubClient(new ProductHeaderValue("MyAmazingApp"));
            var repos = githubClient.Search.SearchRepo(request).Result;
            Console.WriteLine($"ReproCase: Find {repos.TotalCount} repos");

That is becoming to a http request using this url (from Fiddler)
https://api.github.com/search/repositories?page=1&per_page=100&order=desc&q=pushed:2012-11-20T16:00:00+08:00..2012-12-20T16:00:00+08:00

Note that "+" isn't escaped in this case and it only finds zero repositories.

Escaping "+" to "%2B" in a browser gets me total_count 98777

https://api.github.com/search/repositories?page=1&per_page=100&order=desc&q=pushed:2012-11-20T16:00:00%2B08:00..2012-12-20T16:00:00%2B08:00

I attach a .NET core project to demonstrate it.
OctokitRepro.zip

[shiftkey]

@kceiw this sounds like we should be either encoding here

octokit.net/Octokit/Models/Request/SearchRepositoriesRequest.cs

Lines 164 to 167 in e9409e0

	if (Updated != null)
	{
	parameters.Add(string.Format(CultureInfo.InvariantCulture, "pushed:{0}", Updated));
	}

Or more likely inside DateRange itself:

octokit.net/Octokit/Models/Request/SearchRepositoriesRequest.cs

Lines 294 to 300 in fd6bca9

	/// <summary>
	/// helper class in generating the date range values for the date qualifier e.g.
	/// https://help.github.com/articles/searching-repositories#created-and-last-updated
	/// </summary>
	[DebuggerDisplay("{DebuggerDisplay,nq}")]
	public class DateRange
	{

Marking this one as Up for Grabs because I think once we confirm the encoding change this is an easy fix to verify.