app/controllers/items_controller.rb: Downcase MD5 before compare it.
Generate migration AddOnHoldToItems.
db/schema.rb: Update.
app/controllers/items_controller.rb: Add :on_hold to strong parameters.
Add checkbox for :on_hold to new/edit page.
app/views/items/show.html.erb: Display status HOLD or OPEN.
Display status in items page.
Hide status if user not signed in, in items page.