Support for multiple LTI accounts using the same email address

From Blackboard, it is not possible to test an Evalmee exam using a test account.

A test account can dynamically create a new user with the same email address as the original account (but with a different ID : "lis_person_sourcedid"=>"utilisateur@ecole.com_previewuser)

Therefore, this test account cannot be used due to the email uniqueness check.