Track total assets cache size in Live Dashboard

lib/music_library_web/telemetry.ex

@@ -115,6 +115,9 @@ defmodule MusicLibraryWeb.Telemetry do
         ]
       ),
 
+      # Assets
+      summary("music_library.assets.cache.total_content_size", unit: {:byte, :kilobyte}),
+
       # VM Metrics
       summary("vm.memory.total", unit: {:byte, :megabyte}),
       summary("vm.total_run_queue_lengths.total"),
@@ -125,6 +128,7 @@ defmodule MusicLibraryWeb.Telemetry do
 
   defp periodic_measurements do
     [
+      {MusicLibrary.Assets.Cache, :track_total_content_size, []}
       # A module, function and arguments to be invoked periodically.
       # This function must call :telemetry.execute/3 and a metric must be added above.
       # {MusicLibraryWeb, :count_users, []}