Add confirmation to flush the whole page cache

(cherry picked from commit ba4f133)

# Conflicts:
#	app/views/alchemy/admin/pages/_toolbar.html.erb

Author: tvdeyen

app/views/alchemy/admin/pages/_toolbar.html.erb

@@ -23,8 +23,9 @@
           alchemy.flush_admin_pages_path,
           remote: true,
           method: :post,
-          class: "icon_button please_wait",
-          title: Alchemy.t("Flush page cache")
+          class: "icon_button",
+          title: Alchemy.t("Flush page cache"),
+          "data-turbo-confirm": Alchemy.t(:confirm_to_flush_cache)
         ) %>
       </sl-tooltip>
     </div>

config/locales/alchemy.en.yml

@@ -391,6 +391,7 @@ en:
     confirm_to_delete_menu: "Do you really want to delete this menu?"
     confirm_to_delete_node: "Do you really want to delete this menu node?"
     confirm_to_delete_page: "Do you really want to delete this page?"
+    confirm_to_flush_cache: "Do you really want to flush the page cache? This will might take a while and can make first page requests slow."
     ingredient_validations_headline: "Please check marked fields below"
     copy: "copy"
     copy_element: "Copy this element"