Redirect to event instead of registration detail page

[JPustkuchen]

After successfully submitting the registration form the user is being redirected to the detail form of the registration without a link back to the source event.

This doesn't seem the best option for most cases. I'd suggest to add a setting to select whether the user:

1. Is redirected back to the event
2. Is redirected to the registration detail page + add a link to the parent event entity
   (3. Is redirected to a custom (token) path)

What do you think?

[JPustkuchen]

Sorry I think the rng core module is the better place for this issue, so I created an issue there. See dpi/rng#160

But we should keep in mind that the implementation in Drupal\rng_quick\Form\RegisterBlockForm may also be affected with its redirects.