OIDC: use UserHelpers.has_oidc? in index and show

- Index OIDC column and show OIDC item use has_oidc? instead of raw oidc_id.
- Avoids empty string showing as Linked.

lib/mv_web/live/user_live/show.ex

@@ -62,7 +62,9 @@ defmodule MvWeb.UserLive.Show do
             else: gettext("Not enabled")}
         </:item>
         <:item title={gettext("OIDC")}>
-          {if @user.oidc_id, do: gettext("Linked"), else: gettext("Not linked")}
+          {if MvWeb.Helpers.UserHelpers.has_oidc?(@user),
+            do: gettext("Linked"),
+            else: gettext("Not linked")}
         </:item>
         <:item title={gettext("Linked Member")}>
           <%= if @user.member do %>