When we turn on settings automatically for customers,
we sometimes use `.set_and_log` which will make a staff
action log for the site setting change. This is fine, but
there is no context for customers.
This change allows setting a message with `.set_and_log`, which
will be stored in the `details` column of the staff action log
created, which will show up on `/admin/logs/staff_action_logs`
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Co-authored-by: Kelv <kelv@discourse.org>
Martin Brennan