Cross-site authentication options on separate domains
问题 We're considering an authentication system for a very temporary website that needs to authenticate from another site. To sum it up here, we have two sites on completely different domains. foo.com is the main site that will always exist (and already does). This is the main place where users go and log into that site, and do things in their logged in state there. That site will get modified soon to have a link to bar.com. When a user that's logged in on foo.com clicks the link to bar.com they