A change introduced in #6125 prevents
`Devise::Models::Confirmable#confirm` from being called for existing
users, which in turn leads to `email` not being set to
`unconfirmed_email`, breaking email updates. This also adds a test
that would've caught this issue.

When a new user confirms their e-mail, bootstrap their home timeline
by automatically following a set of accounts. By default, all local
admin accounts (that are unlocked). Can be customized by new admin
setting (comma-separated usernames, local and unlocked only)