Add response status codes to Plug samples

[jeffkreeftmeijer]

Like appsignal/appsignal-ruby#183, but for Elixir. As requested via support (private Intercom link). Opening this pull request instead of an issue since the implementation was mostly done answering their question.

I recommend tagging samples manually until we merge this. That would look something like this;

defmodule AppsignalPhoenixExampleWeb.PageController do
  use AppsignalPhoenixExampleWeb, :controller

  def index(conn, _params) do
    conn = render(conn, "index.html")
    Appsignal.Transaction.set_sample_data("tags", %{status: to_string(conn.status)})
    conn
  end
end

When using the temporary solution: Some things to note is to update the conn with the result of your render/2 call to make sure the response code is set. Also; don’t forget to return the conn from your action, as Appsignal.Transaction.set_sample_data/2 returns the Appsignal.Transaction struct.

[tombruijn]

Is status descriptive enough in the context of an AppSignal transaction? (for when it can be jobs etc)
Would status_code or http_status/http_status_code make more sense in the AppSignal.com UI?

[tombruijn]

Otherwise the code looks good! Tested it and it works 😄