public Set<String> emailAddressesFor(When when) {
        ImmutableSet.Builder<String> addresses = ImmutableSet.builder();
        addresses.addAll(emailAddresses.getOrDefault(when, List.of()));
        for (When include : when.includes)
            addresses.addAll(emailAddressesFor(include));
        return addresses.build();
    }
Returns all email addresses to notify for the given condition.
config-model-api/src/main/java/com/yahoo/config/application/api/Notifications.java