Add flag default-to-user-email
When set for an export config, if the user doesn't have that attribute, their email will be substituted as a default. If any of the values is not a valid email address, they are filtered out.
Closes#29
Reviewed-on: #30
Reviewed-by: June <june@noreply.git.hamburg.ccc.de>
Important: there are changes here to adapt the tests and the Keycloak test realm that are incompatible with the changes in #29. Ultimately, the changes in #29 need to be applied over this.
Configure Keycloak to allow attaching a debugger (localhost:8081).
Add a testing realm with suitable example entries, and explain how to update and export the realm.
Reviewed-on: #27
