Issues a one-time token for SSO authentication. Include this token when redirecting a user to Learningbank.

Flow

1. Request a sign-in token for a user (bound to their email)
2. Redirect the user to Learningbank with the token
3. Learningbank validates the token and signs the user in
4. Token is invalidated - issue a new one for the next login

Note: Each token is single-use and tied to a specific email address. It cannot be reused or used for a different user.