Lock the design to prevent clashes between design and production edits

Lock the design when a designer and a production person may edit it at the same time, so the designer cannot make changes until the admin or design head unlocks it.

1. When a designer and a production person may edit the same design at the same time, lock the design.

2. While locked, the designer cannot make changes.

3. The admin or design head unlocks it and directs the designer to apply the changes requested by the production person.