B/feature/#123

identy_url is no longer primary key for the user, but the creation process relied on the identity_url and created the user with email ''. The email was set later in the authentication process for new users. I changed the email with the identity_url (user is created with email, identity_url is set later in the process). Because if something happens between the creation and the email setting process, no new user can be created (because of unique cosntraint on email).