Is it possible to track user presence from different topic?
<p>I use Phoenix framework for my Elixir application with WebSocket connection. I have two different topics, one for users and other for admins. Admin should see which users are present. I decided to use <code>Presence</code> module from Phoenix. Unfortunately, you can send current <code>Presence</code> state only to socket which start tracking.</p>

<p>Example code:</p>

<pre><code>def join("users", params, socket) do
  socket |&gt; assign(:user_id, params[:user_id])

  send(self, :after_join)
  {:ok, socket}
end

def join("admins", _params, socket) do
  {:ok, socket}
end

def handle_info(:after_join, socket) do
  push(socket, "presence_state", Presence.list(socket))

  {:ok, _} = Presence.track(socket, socket.assigns[:user_id], %{
    online_at: inspect(System.system_time(:seconds))
  })

  {:noreply, socket}
end
</code></pre>

<p>I want to listen for an event in admins' front-end application for presence changes. Is it possible to do it with <code>Phoenix.Presence</code>?</p>