OIDC: use Application config :oidc from runtime.exs for client secret in prod

lib/mv/config.ex

@@ -367,21 +367,23 @@ defmodule Mv.Config do
   @spec oidc_client_secret() :: String.t() | nil
   def oidc_client_secret do
     case Application.get_env(:mv, :oidc) do
-      oidc when is_list(oidc) -> oidc_client_secret_from_config(Keyword.get(oidc, :client_secret))
+      oidc when is_list(oidc) ->
-      _ -> env_or_setting("OIDC_CLIENT_SECRET", :oidc_client_secret)
+        case Keyword.get(oidc, :client_secret) do
-    end
+          nil ->
-  end
+            env_or_setting("OIDC_CLIENT_SECRET", :oidc_client_secret)
 
-  defp oidc_client_secret_from_config(nil),
+          secret when is_binary(secret) ->
-    do: env_or_setting("OIDC_CLIENT_SECRET", :oidc_client_secret)
-
-  defp oidc_client_secret_from_config(secret) when is_binary(secret) do
             s = String.trim(secret)
             if s != "", do: s, else: env_or_setting("OIDC_CLIENT_SECRET", :oidc_client_secret)
+
+          _ ->
+            env_or_setting("OIDC_CLIENT_SECRET", :oidc_client_secret)
         end
 
-  defp oidc_client_secret_from_config(_),
+      _ ->
-    do: env_or_setting("OIDC_CLIENT_SECRET", :oidc_client_secret)
+        env_or_setting("OIDC_CLIENT_SECRET", :oidc_client_secret)
+    end
+  end
 
   @doc """
   Returns the OIDC admin group name (for role sync). ENV first, then Settings.