Sending th optional flag as `trunue` in the POST /api/subscrirs
body will skip sending opt-iconfirmation e-mails to subscribers
and mark list subscriptions in the request a`confirmed`.
In addition to generating HTML forms for selected public lists,
the form page now shows a URL (/subscription/form) that can be
publicly shared to solicit subscriptions. The page lists all
public lists in the database. This page can be disabled on the
Settings UI.