Add request info to HttpException & RateLimitedException (#957)

* Add request info to RateLimitedException

* Remove Promise from interface.

* Add Request to HttpException.

src/Discord.Net.Core/Net/HttpException.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Net;
 
 namespace Discord.Net
@@ -8,11 +8,13 @@ namespace Discord.Net
         public HttpStatusCode HttpCode { get; }
         public int? DiscordCode { get; }
         public string Reason { get; }
+        public IRequest Request { get; }
 
-        public HttpException(HttpStatusCode httpCode, int? discordCode = null, string reason = null)
+        public HttpException(HttpStatusCode httpCode, IRequest request, int? discordCode = null, string reason = null)
             : base(CreateMessage(httpCode, discordCode, reason))
         {
             HttpCode = httpCode;
+            Request = request;
             DiscordCode = discordCode;
             Reason = reason;
         }

src/Discord.Net.Core/Net/IRequest.cs

@@ -0,0 +1,10 @@
+using System;
+
+namespace Discord.Net
+{
+    public interface IRequest
+    {
+        DateTimeOffset? TimeoutAt { get; }
+        RequestOptions Options { get; }
+    }
+}

src/Discord.Net.Core/Net/RateLimitedException.cs

@@ -1,12 +1,15 @@
-using System;
+using System;
 
 namespace Discord.Net
 {
     public class RateLimitedException : TimeoutException
     {
-        public RateLimitedException()
+        public IRequest Request { get; }
+
+        public RateLimitedException(IRequest request)
             : base("You are being rate limited.")
         {
+            Request = request;
         }
     }
 }