ISTWCMS-6545 Create an admin-only option to remove the 'on this site' search

uw_fdsu_theme_resp.theme

@@ -165,7 +165,10 @@ function uw_fdsu_theme_resp_preprocess_region(&$variables) {
 
   // Get the region from variables.
   $region = $variables['elements']['#region'];
-
+  // Set 'search_local' variable if not set.
+  if (!isset($variables['search_local'])) {
+    $variables['search_local'] = theme_get_setting('search_show_local', 'uw_fdsu_theme_resp');
+  }
   // Variables that we want to have access to regardless of region.
   $variables['branding_level'] = theme_get_setting('wcms_branding_level', 'uw_fdsu_theme_resp') ? theme_get_setting('wcms_branding_level', 'uw_fdsu_theme_resp') : 'full';
   // The menu style is set based on selection if the level is 'full'.
@@ -249,6 +252,20 @@ function uw_fdsu_theme_resp_form_system_theme_settings_alter(&$form, FormStateIn
     return;
   }
 
+  // Fieldset for search options.
+  $form['search_options'] = [
+    '#type' => 'details',
+    '#open' => TRUE,
+    '#title' => t('Search options'),
+  ];
+
+  // Search options checkbox field.
+  $form['search_options']['search_show_local'] = [
+    '#type' => 'checkbox',
+    '#title' => t("Show the 'on this site' search option"),
+    '#default_value' => theme_get_setting('search_show_local', 'uw_fdsu_theme_resp') ?? TRUE,
+  ];
+
   // Fieldset for colour scheme.
   $form['colour_scheme'] = [
     '#type' => 'details',