/auth/link and /auth/upgrade become /auth/google/connect?access=identity|read|write: one handler, one
table of what each access asks Google for, the same callback markers. An unknown access is refused
(422) instead of quietly meaning read, and an instance without Google answers ?link=error for a
grant too, not a silent return to the app. The frontend builds the URL in lib/googleConnect, and a
contract test holds it to the backend route and its access values.
peter
6645caa157