chore: Credo and explain callback limitations

lib/medical_transcription/transcription_server.ex

@@ -10,6 +10,12 @@ defmodule MedicalTranscription.TranscriptionServer do
 
   @impl GenServer
   def init(init_arg) do
+    # NOTE: The rule is: don't do anything slow or risky in your GenServer's init function.
+    # But that isn't always practical. GenServers have a reasonably elegant solution to this: handle_continue/2.
+    # We can change our init function to return {:ok, INTIAL_STATE, {:continue, CONTINUE_TYPE}} which will both
+    # unblock the initialization and guarantee that handle_continue/2 is called before any other message is processed.
+    #
+    # Explanation from: https://www.openmymind.net/Elixir-A-Little-Beyond-The-Basics-Part-8-genservers
     {:ok, init_arg, {:continue, :start}}
   end
 
@@ -24,11 +30,11 @@ defmodule MedicalTranscription.TranscriptionServer do
     {:noreply, state}
   end
 
-  def handle_info({:summary, result}, state) do
+  def handle_info({:summary, _result}, state) do
     {:noreply, state}
   end
 
-  def handle_info(:finished, state) do
+  def handle_info(:finished, _state) do
     {:stop, :shutdown, "Transcription finished"}
   end