implement update-search-url in nera package.

This enables the site's back-end to update the search-url slot in the
site-settings class and database.

src/nera.lisp

@@ -25,6 +25,7 @@
 	   #:set-home-page
 	   #:update-enable-site-logo-setting
 	   #:update-site-name
+           #:update-search-url
 	   #:create-page
 	   #:update-page
 	   #:get-page
@@ -245,6 +246,13 @@ editted article entry as the first item in the list.."
       (setf (site-settings::home-page-of settings-to-update) value)
       (mito:save-dao settings-to-update))))
 
+(defun update-search-url (search-url)
+  "Sets the page (in /storage/pages) to be displayed on the sites home page."
+  (with-connection (db)
+    (let ((settings-to-update (mito:find-dao 'site-settings)))
+      (setf (site-settings::search-url-of settings-to-update) search-url)
+      (mito:save-dao settings-to-update))))
+
 (defun update-site-name (name)
   "Updates the website's `SITE-NAME' the database."
   (with-connection (db)