refactor: cache own user ID in IDiscordCache

- remove Cluster.User
- remove Cluster.Application (it was only being used as an alternative to Cluster.User for some reason)
- move Bot.PermissionsIn to DiscordCacheExtensions

Myriad/Cache/DiscordCacheExtensions.cs

@@ -1,7 +1,9 @@
 using System.Linq;
 using System.Threading.Tasks;
 
+using Myriad.Extensions;
 using Myriad.Gateway;
+using Myriad.Types;
 
 namespace Myriad.Cache
 {
@@ -11,6 +13,8 @@ namespace Myriad.Cache
         {
             switch (evt)
             {
+                case ReadyEvent ready:
+                    return cache.SaveOwnUser(ready.User.Id);
                 case GuildCreateEvent gc:
                     return cache.SaveGuildCreate(gc);
                 case GuildUpdateEvent gu:
@@ -102,5 +106,20 @@ namespace Myriad.Cache
             foreach (var thread in evt.Threads)
                 await cache.SaveChannel(thread);
         }
+
+        public static async Task<PermissionSet> PermissionsIn(this IDiscordCache cache, ulong channelId)
+        {
+            var channel = await cache.GetRootChannel(channelId);
+
+            if (channel.GuildId != null)
+            {
+                var userId = await cache.GetOwnUser();
+                var member = await cache.TryGetSelfMember(channel.GuildId.Value);
+                return await cache.PermissionsFor(channelId, userId, member);
+            }
+
+            return PermissionSet.Dm;
+        }
+
     }
 }

Myriad/Cache/IDiscordCache.cs

@@ -7,6 +7,7 @@ namespace Myriad.Cache
 {
     public interface IDiscordCache
     {
+        public ValueTask SaveOwnUser(ulong userId);
         public ValueTask SaveGuild(Guild guild);
         public ValueTask SaveChannel(Channel channel);
         public ValueTask SaveUser(User user);
@@ -19,6 +20,7 @@ namespace Myriad.Cache
         public ValueTask RemoveUser(ulong userId);
         public ValueTask RemoveRole(ulong guildId, ulong roleId);
 
+        public Task<ulong> GetOwnUser();
         public Task<Guild?> TryGetGuild(ulong guildId);
         public Task<Channel?> TryGetChannel(ulong channelId);
         public Task<Channel?> TryGetDmChannel(ulong userId);

Myriad/Cache/MemoryDiscordCache.cs

@@ -16,6 +16,7 @@ namespace Myriad.Cache
         private readonly ConcurrentDictionary<ulong, Role> _roles = new();
         private readonly ConcurrentDictionary<ulong, User> _users = new();
         private readonly ConcurrentDictionary<ulong, GuildMemberPartial> _guildMembers = new();
+        private ulong? _ownUserId { get; set; }
 
         public ValueTask SaveGuild(Guild guild)
         {
@@ -46,6 +47,15 @@ namespace Myriad.Cache
             }
         }
 
+        public ValueTask SaveOwnUser(ulong userId)
+        {
+            // this (hopefully) never changes at runtime, so we skip out on re-assigning it
+            if (_ownUserId == null)
+                _ownUserId = userId;
+
+            return default;
+        }
+
         public ValueTask SaveUser(User user)
         {
             _users[user.Id] = user;
@@ -125,6 +135,8 @@ namespace Myriad.Cache
             return default;
         }
 
+        public Task<ulong> GetOwnUser() => Task.FromResult(_ownUserId!.Value);
+
         public ValueTask RemoveRole(ulong guildId, ulong roleId)
         {
             _roles.TryRemove(roleId, out _);