- Removed NadekoCommand and Aliases attribute from all commands

- All commands must be marked as partial
- Added [Cmd] Attribute to all commands
- Cmd Attribute comes from the source generator which adds [NadekoCommand] and [Aliases] Attribute to each command
- Should be updated in the future probably to be more performant and maybe add extra data to the commands
- Started reorganizing modules and submodules

src/NadekoBot/Modules/Administration/Timezone/GuildTimezoneService.cs

@@ -0,0 +1,77 @@
+#nullable disable
+using NadekoBot.Db;
+using NadekoBot.Services.Database.Models;
+
+namespace NadekoBot.Modules.Administration.Services;
+
+public class GuildTimezoneService : INService
+{
+    public static ConcurrentDictionary<ulong, GuildTimezoneService> AllServices { get; } = new();
+    private readonly ConcurrentDictionary<ulong, TimeZoneInfo> _timezones;
+    private readonly DbService _db;
+
+    public GuildTimezoneService(DiscordSocketClient client, Bot bot, DbService db)
+    {
+        _timezones = bot.AllGuildConfigs.Select(GetTimzezoneTuple)
+                        .Where(x => x.Timezone != null)
+                        .ToDictionary(x => x.GuildId, x => x.Timezone)
+                        .ToConcurrent();
+
+        var curUser = client.CurrentUser;
+        if (curUser != null)
+            AllServices.TryAdd(curUser.Id, this);
+        _db = db;
+
+        bot.JoinedGuild += Bot_JoinedGuild;
+    }
+
+    private Task Bot_JoinedGuild(GuildConfig arg)
+    {
+        var (guildId, tz) = GetTimzezoneTuple(arg);
+        if (tz != null)
+            _timezones.TryAdd(guildId, tz);
+        return Task.CompletedTask;
+    }
+
+    private static (ulong GuildId, TimeZoneInfo Timezone) GetTimzezoneTuple(GuildConfig x)
+    {
+        TimeZoneInfo tz;
+        try
+        {
+            if (x.TimeZoneId is null)
+                tz = null;
+            else
+                tz = TimeZoneInfo.FindSystemTimeZoneById(x.TimeZoneId);
+        }
+        catch
+        {
+            tz = null;
+        }
+
+        return (x.GuildId, Timezone: tz);
+    }
+
+    public TimeZoneInfo GetTimeZoneOrDefault(ulong guildId)
+    {
+        if (_timezones.TryGetValue(guildId, out var tz))
+            return tz;
+        return null;
+    }
+
+    public void SetTimeZone(ulong guildId, TimeZoneInfo tz)
+    {
+        using var uow = _db.GetDbContext();
+        var gc = uow.GuildConfigsForId(guildId, set => set);
+
+        gc.TimeZoneId = tz?.Id;
+        uow.SaveChanges();
+
+        if (tz is null)
+            _timezones.TryRemove(guildId, out tz);
+        else
+            _timezones.AddOrUpdate(guildId, tz, (key, old) => tz);
+    }
+
+    public TimeZoneInfo GetTimeZoneOrUtc(ulong guildId)
+        => GetTimeZoneOrDefault(guildId) ?? TimeZoneInfo.Utc;
+}