action.exs

defmodule Action do
  defmodule Configuration do
  end

  @callback description(Configuration) :: String
  @callback perform(Configuration, String) :: nil
end

defmodule Webhook do
  @behaviour Action

  defmodule Configuration do
    defstruct url: nil, method: "POST"
  end

  def description(%Configuration{url: url}) do
    ~s(Sends a text to '#{url}'.)
  end

  def perform(Configuration, text) do
    text
  end
end

config = %Webhook.Configuration{url: "http://httpbin.org"}