* When adding collaborators, you don't need a custom role. If you don't choose
one, a basic default "developer" role will be used
* If you don't assign a `ProjectCollabUser` role, a default "user" role is
assumed for logged in users, otherwise a "guest" role
* The "guest" role currently has no access at all
* Theoretically there may also be a "maintainer" role allowing project
sharers/maintainers to give maintainer-level access to more people, but right
now maintainer role would be the same as developer so I haven't added it yet
