duplicate user detection

[baszoetekouw]

When an IdP gets a new entityid, EduTEAMS considers all users from the IdP as new users and wil create new cuids from them. Therefore, also SBS considers them fresh, new users.

This leads to a lot of confusion for users, because they seemingly can log in correctly, but have lost all CO memberships.

So instead I would like to propose that SBS refuses to create two users with identical email addresses. If that happens, we need to show an error page instead, asking the user to contact sram-support, and also sending an error mail to sram-beheer.

But what about eduid users?

Needs to be solved in relation to account linking/migration.

Park for now.