Clearer courier setup and a way to hide one for a while

Setting up a courier is clearer now. First you enter only the access data and connect the courier; only then do parcel handover, pricing and payment methods appear. There's no separate "Enable" step - once a courier is connected, has a price and your sender address is filled in, it's offered to your customers automatically. A new Hide toggle lets you temporarily take a ready courier off checkout (a lapsed contract, say) without deleting its settings.