Test-driving the two user sessions crashes (as one might already expect while refactoring for the Lifecycle part) because the returned session handle from the new take_quiz function is not a :via tuple, yet it is passed directly to GenServer.call in the deliberately unchanged select_question and answer_question functions.

As long as we do not want API users to have to call Mastery.Boundary.QuizSession.via themselves, we should either call it in the two mentioned API functions before calling GenServer, or just return a :via tuple as the session token, which I think is easier:

def take_quiz(title, email) do
  with %Quiz{}=quiz <- QuizManager.lookup_quiz_by_title(title),
       {:ok, _} <- QuizSession.take_quiz(quiz, email)
  do
    QuizSession.via({title, email}) 
  else
    error -> error
  end
end