Split out unmanaged implementation of RealmLive into its own class

osu.Game/Database/RealmLiveUnmanaged.cs

@@ -0,0 +1,44 @@
+// 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;
+using Realms;
+
+#nullable enable
+
+namespace osu.Game.Database
+{
+    /// <summary>
+    /// Provides a method of working with unmanaged realm objects.
+    /// Usually used for testing purposes where the instance is never required to be managed.
+    /// </summary>
+    /// <typeparam name="T">The underlying object type.</typeparam>
+    public class RealmLiveUnmanaged<T> : ILive<T> where T : RealmObjectBase, IHasGuidPrimaryKey
+    {
+        /// <summary>
+        /// Construct a new instance of live realm data.
+        /// </summary>
+        /// <param name="data">The realm data.</param>
+        public RealmLiveUnmanaged(T data)
+        {
+            Value = data;
+        }
+
+        public bool Equals(ILive<T>? other) => ID == other?.ID;
+
+        public Guid ID => Value.ID;
+
+        public void PerformRead(Action<T> perform) => perform(Value);
+
+        public TReturn PerformRead<TReturn>(Func<T, TReturn> perform) => perform(Value);
+
+        public void PerformWrite(Action<T> perform) => throw new InvalidOperationException(@"Can't perform writes on a non-managed underlying value");
+
+        public bool IsManaged => false;
+
+        /// <summary>
+        /// The original live data used to create this instance.
+        /// </summary>
+        public T Value { get; }
+    }
+}