Ref T8116. A package has:
- a publisher (like "Phacility"), from the previous revision;
- a name (like "Arcanist");
- a package key (like "arcanist").
The package key is immutable, like the publisher key.
This gives a package a full key like "phacility/arcanist".
Policy stuff:
- You must be able to view a publisher to view a package (currently, everyone can always see all publishers).
- You must be able to edit a publisher to create a new package inside it.
- Packages have separate view/edit permissions.
This still does nothing interesting.
