For machines that have Linux MD RAID arrays, I want to receive
notifications about the status of the arrays immediately via _ntfy_. I
had this before with `journal2ntfy`, but I never got around to setting
it up for the current generation of machines (_nvr2_, _chromie_). Now
that we have `fluent-bit` deployed, we can use its pipeline capabilities
to select the subset of messages for which we want immediate alerts and
send them directly to _ntfy_. We use a Lua function to transform the
log record into a body compatible with _ntfy_'s JSON publish request;
`fluent-bit` doesn't have any other way to set array values, as needed
for the `tags` member.