Signing in from a sister site
How it fits together

Signing in from a sister site

You open the research site while signed out and press Sign in.

Description
  1. The site sends you to the hub's login page and tells it where to send you back. The hub only sends you back to a site that is in its registry of sites.
  2. The hub's login page talks to Hydra through the backend. Hydra issues the session, and the backend sets the refresh cookie and the central cookie that says you are signed in.
  3. The research site's header asks the hub whether you are signed in, the hub reads its central cookie and answers, and the site completes a session of its own.