feat(secrets): updated as recommended in ashauthentication docs

lib/mv/secrets.ex

@@ -0,0 +1,26 @@
+defmodule Mv.Secrets do
+  use AshAuthentication.Secret
+
+  def secret_for([:authentication, :strategies, :rauthy, :client_id], Mv.Accounts.User, _opts, _meth) do
+    get_config(:client_id)
+  end
+
+  def secret_for([:authentication, :strategies, :rauthy, :redirect_uri], Mv.Accounts.User, _opts, _meth) do
+    get_config(:redirect_uri)
+  end
+
+  def secret_for([:authentication, :strategies, :rauthy, :client_secret], Mv.Accounts.User, _opts, _meth) do
+    get_config(:client_secret)
+  end
+
+  def secret_for([:authentication, :strategies, :rauthy, :base_url], Mv.Accounts.User, _opts, _meth) do
+    get_config(:base_url)
+  end
+
+  defp get_config(key) do
+    :mv
+    |> Application.fetch_env!(:rauthy)
+    |> Keyword.fetch!(key)
+    |> then(&{:ok, &1})
+  end
+end