Change GuildMemberUpdate before to cacheable

src/Discord.Net.WebSocket/BaseSocketClient.Events.cs

@@ -347,12 +347,11 @@ namespace Discord.WebSocket
         }
         internal readonly AsyncEvent<Func<SocketUser, SocketUser, Task>> _userUpdatedEvent = new AsyncEvent<Func<SocketUser, SocketUser, Task>>();
         /// <summary> Fired when a guild member is updated, or a member presence is updated. </summary>
-        /// <remarks> The first user (state before) might be null if they weren't in the cache. </remarks>
-        public event Func<SocketGuildUser, SocketGuildUser, Task> GuildMemberUpdated {
+        public event Func<Cacheable<SocketGuildUser, ulong>, SocketGuildUser, Task> GuildMemberUpdated {
             add { _guildMemberUpdatedEvent.Add(value); }
             remove { _guildMemberUpdatedEvent.Remove(value); }
         }
-        internal readonly AsyncEvent<Func<SocketGuildUser, SocketGuildUser, Task>> _guildMemberUpdatedEvent = new AsyncEvent<Func<SocketGuildUser, SocketGuildUser, Task>>();     
+        internal readonly AsyncEvent<Func<Cacheable<SocketGuildUser, ulong>, SocketGuildUser, Task>> _guildMemberUpdatedEvent = new AsyncEvent<Func<Cacheable<SocketGuildUser, ulong>, SocketGuildUser, Task>>();     
         /// <summary> Fired when a user joins, leaves, or moves voice channels. </summary>
         public event Func<SocketUser, SocketVoiceState, SocketVoiceState, Task> UserVoiceStateUpdated {
             add { _userVoiceStateUpdatedEvent.Add(value); }

src/Discord.Net.WebSocket/DiscordSocketClient.cs

@@ -988,12 +988,15 @@ namespace Discord.WebSocket
 
                                             var before = user.Clone();
                                             user.Update(State, data);
-                                            await TimedInvokeAsync(_guildMemberUpdatedEvent, nameof(GuildMemberUpdated), before, user).ConfigureAwait(false);
+
+                                            var cacheableBefore = new Cacheable<SocketGuildUser, ulong>(before, user.Id, true, () => Task.FromResult((SocketGuildUser)null));
+                                            await TimedInvokeAsync(_guildMemberUpdatedEvent, nameof(GuildMemberUpdated), cacheableBefore, user).ConfigureAwait(false);
                                         }
                                         else
                                         {
                                             user = guild.AddOrUpdateUser(data);
-                                            await TimedInvokeAsync(_guildMemberUpdatedEvent, nameof(GuildMemberUpdated), null, user).ConfigureAwait(false);
+                                            var cacheableBefore = new Cacheable<SocketGuildUser, ulong>(null, user.Id, false, () => Task.FromResult((SocketGuildUser)null));
+                                            await TimedInvokeAsync(_guildMemberUpdatedEvent, nameof(GuildMemberUpdated), cacheableBefore, user).ConfigureAwait(false);
                                         }
                                     }
                                     else