More minor restructuring and cleanup. Most modules and submodules should be properly grouped now

src/NadekoBot/Modules/Permissions/PermissionsCollection.cs

@@ -0,0 +1,77 @@
+#nullable disable
+using NadekoBot.Common.Collections;
+using NadekoBot.Services.Database.Models;
+
+namespace NadekoBot.Modules.Permissions.Common;
+
+public class PermissionsCollection<T> : IndexedCollection<T>
+    where T : class, IIndexed
+{
+    public override T this[int index]
+    {
+        get => Source[index];
+        set
+        {
+            lock (_localLocker)
+            {
+                if (index == 0) // can't set first element. It's always allow all
+                    throw new IndexOutOfRangeException(nameof(index));
+                base[index] = value;
+            }
+        }
+    }
+
+    private readonly object _localLocker = new();
+
+    public PermissionsCollection(IEnumerable<T> source)
+        : base(source)
+    {
+    }
+
+    public static implicit operator List<T>(PermissionsCollection<T> x)
+        => x.Source;
+
+    public override void Clear()
+    {
+        lock (_localLocker)
+        {
+            var first = Source[0];
+            base.Clear();
+            Source[0] = first;
+        }
+    }
+
+    public override bool Remove(T item)
+    {
+        bool removed;
+        lock (_localLocker)
+        {
+            if (Source.IndexOf(item) == 0)
+                throw new ArgumentException("You can't remove first permsission (allow all)");
+            removed = base.Remove(item);
+        }
+
+        return removed;
+    }
+
+    public override void Insert(int index, T item)
+    {
+        lock (_localLocker)
+        {
+            if (index == 0) // can't insert on first place. Last item is always allow all.
+                throw new IndexOutOfRangeException(nameof(index));
+            base.Insert(index, item);
+        }
+    }
+
+    public override void RemoveAt(int index)
+    {
+        lock (_localLocker)
+        {
+            if (index == 0) // you can't remove first permission (allow all)
+                throw new IndexOutOfRangeException(nameof(index));
+
+            base.RemoveAt(index);
+        }
+    }
+}