Issue #3455716 by pfrenssen: Provide a default value for the registration type

.gitlab-ci.yml

composer.json

...ring_events_series/group_recurring_events_series.info.yml

modules/recurring_events_ical/recurring_events_ical.info.yml

...ring_events_reminders/recurring_events_reminders.info.yml

...vents_registration/recurring_events_registration.info.yml

...s/recurring_events_registration/src/Entity/Registrant.php

...curring_events_registration/src/Enum/RegistrationType.php

...es/recurring_events_registration/src/Form/ContactForm.php

...recurring_events_registration/src/Form/RegistrantForm.php

...on/src/Plugin/views/field/EventSeriesRegistrationType.php

...curring_events_registration/src/RegistrantListBuilder.php

...g_events_registration/src/RegistrationCreationService.php

...g_events_registration/tests/src/Kernel/RegistrantTest.php

...es/recurring_events_views/recurring_events_views.info.yml

recurring_events.info.yml