Where to add the event handlers?

event_handler.ex

defmodule KV.Supervisor do
  use Supervisor

  def start_link do
    Supervisor.start_link(__MODULE__, :ok)
  end

  @manager_name KV.EventManager
  @registry_name KV.Registry

  def init(:ok) do
    children = [
      worker(GenEvent, [[name: @manager_name]]),
      worker(KV.Registry, [@manager_name, [name: @registry_name]])
    ]

    supervise(children, strategy: :one_for_one)
  end
end