Update: Added RelayServer Logic

RelayServer/Services/CoreClientService.cs

@@ -0,0 +1,16 @@
+namespace RelayServer.Services;
+
+public sealed class CoreClientService
+{
+    public Task<CoreUser?> GetUserByUsernameAsync(string username)
+    {
+        return Task.FromResult<CoreUser?>(username switch
+        {
+            "Keeper317" => new CoreUser("users:keeper317", "Keeper317", true),
+            "Ru_Kira" => new CoreUser("users:ru_kira", "Ru_Kira", true),
+            _ => null
+        });
+    }
+}
+
+public sealed record CoreUser(string Id, string Username, bool Licensed);