Depends on D20278. Ref T5474. This change creates some new empty objects that do nothing, and some new views for looking at those objects. There's no actual useful behavior yet.
The "Edit" controller is custom instead of being driven by "EditEngine" because I expect it to be a Herald-style "add new rules" UI, and EditEngine isn't a clean match for those today (although maybe I'll try to move it over).
The general idea here is:
- Triggers are "real" objects with a real PHID.
- Each trigger has a name and a collection of rules, like "Change status to: X" or "Play sound: Y".
- Each column may be bound to a trigger.
- Multiple columns may share the same trigger.
- Later UI refinements will make the cases around "copy trigger" vs "reference the same trigger" vs "create a new ad-hoc trigger" more clear.
- Triggers have their own edit policy.
- Triggers are always world-visible, like Herald rules.