Refactor Games, support reading Rich Presences (#877)

* Add API-level support for Rich Presences

* Add library-level support for Game presences

* Add model conversions for outgoing+incoming rich presences

* Refactored Game into Activities

* Integrated Activities with user entities

rebase hell from 5f3cb947a92f4fd01cc4df47ca548180036b47f3

* Fix JSON converters for Activities

* Finish rebase, activity should be set on BaseSocketClient

* Use ApplicationId to define a rich presence

* Added SetActivityAsync to Base and Sharded Socket clients

* Remove public parameterless Game constructor

* Remove GameAssets, refactored to GameAsset

* Hide constructors for types that should be read-only

* Revert changes to Discord.Net.sln

got damned visual studio caching

* Refactor GameParty to use dedicated current/capacity values

Per feedback from @khionu

src/Discord.Net.Rest/API/Common/Game.cs

@@ -13,6 +13,22 @@ namespace Discord.API
         public Optional<string> StreamUrl { get; set; }
         [JsonProperty("type")]
         public Optional<StreamType?> StreamType { get; set; }
+        [JsonProperty("details")]
+        public Optional<string> Details { get; set; }
+        [JsonProperty("state")]
+        public Optional<string> State { get; set; }
+        [JsonProperty("application_id")]
+        public Optional<ulong> ApplicationId { get; set; }
+        [JsonProperty("assets")]
+        public Optional<API.GameAssets> Assets { get; set; }
+        [JsonProperty("party")]
+        public Optional<API.GameParty> Party { get; set; }
+        [JsonProperty("secrets")]
+        public Optional<API.GameSecrets> Secrets { get; set; }
+        [JsonProperty("timestamps")]
+        public Optional<API.GameTimestamps> Timestamps { get; set; }
+        [JsonProperty("instance")]
+        public Optional<bool> Instance { get; set; }
 
         [OnError]
         internal void OnError(StreamingContext context, ErrorContext errorContext)

src/Discord.Net.Rest/API/Common/GameAssets.cs

@@ -0,0 +1,16 @@
+using Newtonsoft.Json;
+
+namespace Discord.API
+{
+    internal class GameAssets
+    {
+        [JsonProperty("small_text")]
+        public Optional<string> SmallText { get; set; }
+        [JsonProperty("small_image")]
+        public Optional<string> SmallImage { get; set; }
+        [JsonProperty("large_image")]
+        public Optional<string> LargeText { get; set; }
+        [JsonProperty("large_text")]
+        public Optional<string> LargeImage { get; set; }
+    }
+}

src/Discord.Net.Rest/API/Common/GameParty.cs

@@ -0,0 +1,12 @@
+using Newtonsoft.Json;
+
+namespace Discord.API
+{
+    internal class GameParty
+    {
+        [JsonProperty("id")]
+        public string Id { get; set; }
+        [JsonProperty("size")]
+        public int[] Size { get; set; }
+    }
+}

src/Discord.Net.Rest/API/Common/GameSecrets.cs

@@ -0,0 +1,14 @@
+using Newtonsoft.Json;
+
+namespace Discord.API
+{
+    internal class GameSecrets
+    {
+        [JsonProperty("match")]
+        public string Match { get; set; }
+        [JsonProperty("join")]
+        public string Join { get; set; }
+        [JsonProperty("spectate")]
+        public string Spectate { get; set; }
+    }
+}

src/Discord.Net.Rest/API/Common/GameTimestamps.cs

@@ -0,0 +1,15 @@
+using System;
+using Newtonsoft.Json;
+
+namespace Discord.API
+{
+    internal class GameTimestamps
+    {
+        [JsonProperty("start")]
+        [UnixTimestamp]
+        public Optional<DateTimeOffset> Start { get; set; }
+        [JsonProperty("end")]
+        [UnixTimestamp]
+        public Optional<DateTimeOffset> End { get; set; }
+    }
+}

src/Discord.Net.Rest/API/UnixTimestampAttribute.cs

@@ -0,0 +1,7 @@
+using System;
+
+namespace Discord.API
+{
+    [AttributeUsage(AttributeTargets.Property)]
+    internal class UnixTimestampAttribute : Attribute { }
+}