Control price visibility

[EmlynC]

I want to merge this change because I'd like to able to control the visibility of prices for products. Either prices are publicly available, for registered customers or for staff only.

There are a few reasons for this feature:

• Businesses that cannot publicly publish prices, can choose to only shown prices to known users.
• Once a user is shown a price, there is an obligation to offer that price. This allows for more protection over publicly showing the price.
• Businesses that have complex products and allow users to 'shop' for products before getting a price quoted to them.

The feature isn't finished as it requires support on the GraphQL API, which would require field-level permissions. PWA support can be added, but it's probably best to get some agreement on what a user would see if the price is unavailable; show "Price unavailable" or a "Ask a question" etc.

Tasks outstanding

• Remove price from cart
• Remove price from checkout
• API support i.e. price not shown if user can't request it
• PWA support
• Dashboard 2.0 support

Screenshots

If a user does not have permission to see the price, the following is shown:

Dashboard edit view:

Dashboard detail view:

Pull Request Checklist

1. Privileged views and APIs are guarded by proper permission checks.
2. All visible strings are translated with proper context.
3. All data-formatting is locale-aware (dates, numbers, and so on).
4. Database queries are optimized and the number of queries is constant.
5. Database migration files are up to date.
6. The changes are tested.
7. The code is documented (docstrings, project documentation).
8. GraphQL schema and type definitions are up to date.
9. Changes are mentioned in the changelog.

[EmlynC]

Old dashboard — will raise a separate PR for dashboard-next