Router BeforeNavigationEvent::reRouteToError

[pleku]

Add following methods to BeforeNavigationEvent

void rerouteToError(Class<? extends Exception> clazz)
void rerouteToError(Class<? extends Exception> clazz, String errorMessage)

public class AuthenticationHandler implements BeforeNavigationListener {
  @Override
  public void beforeNavigation(BeforeNavigationEvent event) {
    Class<?> target = event.getNavigationTarget();
    if (!currentUserMayEnter(target)) {
      event.rerouteToError(AccessDeniedException.class);
    }
  }
}

Add a mention of this API to the documentation.

Waits for #2346