refactor: restructure interaction system into clean layers

src/Shared/Domain/InstanceId.cs

@@ -0,0 +1,15 @@
+using System;
+using System.Security.Cryptography;
+using System.Text;
+
+namespace Game.Shared.Domain;
+
+public readonly record struct InstanceId(Guid Value)
+{
+    private static Guid CreateDeterministicId(string source) =>
+        new(MD5.HashData(Encoding.UTF8.GetBytes(source)));
+
+    public static InstanceId FromKey(string key) => new(CreateDeterministicId(key));
+
+    public override string ToString() => Value.ToString();
+}