Placeholder for displayed price when using pricing phase

Headline:
Show placeholder instead of price on order form when task is calculating pricing


Description:
As per the suggestion here, lookups from an external system via a task can be slow to generate pricing and show incorrect prices on the order form for a selected configuration. Instead, use a placeholder on the order form to show “calculating prices” or similar when the plan/configuration is changed rather than the old price.
Additionally, don’t allow the user to click “Next” until a price has been obtained - it is possible to select a “cheap” plan, then switch to an expensive one and click next before the pricing task has completed and the order summary shows the expensive plan but with the cheap price.


Example/Use case(s):
User selects plan → Pricing phase task (python) runs but takes a few seconds to complete → Form shows selected plan but with an incorrect cost → User clicks next → Order summary shows incorrect price for plan


This is the original post but a duplicate of a further explained post here. Closing this and migrating to the other post.