Add is_locked field on the Product model #310

[tdruez]

Changes:

• A new is_locked "Locked inventory" added to the ProductStatus model

When is_locked=True status is set on a Product:

• In the Product list: A "lock" icon is displayed with "Inventory is locked" as title
• In the Product details: a warning is displayed on top of the page: "This product version is marked as read-only, preventing any modifications to its inventory."
• In the Product details: The "Manage" and "Action" dropdown are disabled
• In the Product details Inventory/Hierarchy tabs: All the "edit" and "delete" link icons are hidden
• In the Package/Component list and details view, the "Add to Product" will not list the "locked" Products.

[DennisClark]

@tdruez Everything looks good and works fine in Staging, both nexB and Starship. Your help text for the new indicator is excellent. No problems found.