test authentication flows that redirect across origins in cypress using cy.origin()

Steps

1. wrap interactions that occur on the secondary domain (e.g. an OAuth provider's login page) in cy.origin(url, () => { ... })
2. pass any data needed inside the callback via the options argument's args property, since the callback runs in an isolated context without closure access to outer variables
3. perform the login form interactions inside the cy.origin() block using standard commands scoped to that secondary origin
4. allow the flow to navigate back to the original origin after authentication completes, then resume normal top-level cy commands
5. combine with cy.session() to cache the resulting authenticated session across tests and avoid repeating the full cross-origin login flow each time