Don't track route not found errors

lib/music_library/error_ignorer.ex

@@ -0,0 +1,18 @@
+defmodule MusicLibrary.ErrorIgnorer do
+  @moduledoc """
+  Ignores errors that should not be tracked by ErrorTracker.
+
+  Bot scanners and crawlers routinely hit non-existent paths, generating
+  NoRouteError exceptions that are not actionable. We ignore them here
+  rather than blocking specific paths in the endpoint.
+  """
+  @behaviour ErrorTracker.Ignorer
+
+  @ignored_kinds [
+    to_string(Phoenix.Router.NoRouteError)
+  ]
+
+  @impl true
+  def ignore?(%ErrorTracker.Error{kind: kind}, _context) when kind in @ignored_kinds, do: true
+  def ignore?(_error, _context), do: false
+end