Display a warning message to shop managers when they choose a config that will prevent checkout

[audez]

What is the need / problem?

Switching all payment or shipping methods to "backoffice only" will prevent customers from checking out. But the shop manager is not aware of this when they change these settings.

Which type of users does this problem affect (and how many, if known)?

- Shoppers
- Hub Managers (MCFEs)

Potential solutions that will solve the problem ?[[brainstorming to list feature candidates]

When the shop manager switch

• the last active shipping method to “Back office only”, or switch all active shipping methods to “Back office only”
• the last active payment method to “Back office only”, or switch all active payment methods to “Back office only”

Display a warning message to the shop manager, as:
“Beware that this configuration will prevent clients from checking out. Only the shopfront will be displayed - clients won’t be able to access the checkout page”

Connected wishlist and discovery discussions* [list precedent discussions]

#273
openfoodfoundation/openfoodnetwork#9614

Additional context

Has been mentioned here