Closed mint connections are not handled.

[nduitz]

Environment

• Pigeon version: main (unreleased)

Current behavior

If the FCM adapter is alive for a while lib/pigeon/fcm.ex:150 won't match since the socket closes and that is never handled properly

Expected behavior

  def handle_info({:closed, _}, %{config: config} = state) do
    case connect_socket(config) do
      {:ok, socket} ->
        Configurable.schedule_ping(config)
        {:noreply, %{state | socket: socket}}

      {:error, reason} ->
        {:stop, reason}
    end
  end

should handle closed connections.