[ifcbrk] feature: Implement Client Status Support (#1247)

* Implement Client Status Support

Adds support for using the client_status as sent as part of the Presence model. This value can be used to determine if a user is active on the native desktop app, the mobile app, or the website.

* lint: whitespace in IPresence

* Remove breaking change to IPresence interface with a note for 2.1

* update comment to not reference 2.1

* re-add interface break to IPresence

* add example payload for client_status

* use inline declaration for Enum.TryParse

src/Discord.Net.Rest/Entities/Users/RestUser.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Immutable;
 using System.Diagnostics;
 using System.Threading.Tasks;
 using Model = Discord.API.User;
@@ -31,6 +32,8 @@ namespace Discord.Rest
         /// <inheritdoc />
         public virtual UserStatus Status => UserStatus.Offline;
         /// <inheritdoc />
+        public virtual IImmutableSet<ClientType> ActiveClients => ImmutableHashSet<ClientType>.Empty;
+        /// <inheritdoc />
         public virtual bool IsWebhook => false;
 
         internal RestUser(BaseDiscordClient discord, ulong id)