Add basic base class to begin to standardise function across caching components

osu.Game/Database/MemoryCachingComponent.cs

@@ -0,0 +1,17 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System.Collections.Concurrent;
+using osu.Framework.Graphics;
+
+namespace osu.Game.Database
+{
+    /// <summary>
+    /// A component which performs lookups (or calculations) and caches the results.
+    /// Currently not persisted between game sessions.
+    /// </summary>
+    public abstract class MemoryCachingComponent<TLookup, TValue> : Component
+    {
+        protected readonly ConcurrentDictionary<TLookup, TValue> Cache = new ConcurrentDictionary<TLookup, TValue>();
+    }
+}