Auto-ban duplicate users when a user is banned

app/models/user.rb

app/models/user_custom_attribute.rb

app/services/users/auto_ban_service.rb

app/services/users/ban_service.rb

app/workers/all_queues.yml

app/workers/anti_abuse/ban_duplicate_users_worker.rb

..._flags/gitlab_com_derisk/auto_ban_via_detumbled_email.yml

config/sidekiq_queues.yml

ee/app/models/ee/abuse_report.rb

ee/app/workers/anti_abuse/new_abuse_report_worker.rb

ee/app/workers/ee/anti_abuse/ban_duplicate_users_worker.rb

.../workers/ee/anti_abuse/ban_duplicate_users_worker_spec.rb

spec/models/user_custom_attribute_spec.rb

spec/models/user_spec.rb

spec/services/users/auto_ban_service_spec.rb

spec/services/users/ban_service_spec.rb

...workers/anti_abuse/ban_duplicate_users_shared_examples.rb

spec/workers/anti_abuse/ban_duplicate_users_worker_spec.rb