add: Added .cleanupguilddata command which will delete all guildconfigs, xp stats and other data related to any guild the bot is no longer in. This is a highly destructive and irreversible command.

dev: Added cascade deletes to any tables which have guildconfigs FK, as well as to some other missing places

src/NadekoBot/Modules/Administration/DangerousCommands/CleanupCommands.cs

@@ -0,0 +1,31 @@
+namespace NadekoBot.Modules.Administration.DangerousCommands;
+
+public partial class Administration 
+{
+    [Group]
+    public class CleanupCommands : CleanupModuleBase
+    {
+        private readonly ICleanupService _svc;
+
+        public CleanupCommands(ICleanupService svc)
+            => _svc = svc;
+
+        [Cmd]
+        [OwnerOnly]
+        [RequireContext(ContextType.DM)]
+        public async Task CleanupGuildData()
+        {
+            var result = await _svc.DeleteMissingGuildDataAsync();
+
+            if (result is null)
+            {
+                await ctx.ErrorAsync();
+                return;
+            }
+
+            await Response()
+                  .Confirm($"{result.GuildCount} guilds' data remain in the database.")
+                  .SendAsync();
+        }
+    }
+}