Journaling: outside archives, and Journal it in mail flow rules

Phase 3 of the journaling spec.

- A journal's destination: builtIn (true for journals stored before) and
  archiveAddress, at least one. Reports to an archive are queued from the
  empty sender, one per address, flagged so they're never journaled.
- A pending record per report. When the queue lets go of one without
  delivering it (refused, expired, deleted), it becomes its own entry in
  the built-in journal under the sending journals' retention, the
  journal's archiveFailures (count, last time, reason) goes up, and the
  audit log records it; if that can't be written it stays queued.
- Journal it: a rule action naming a journal, on mail flow rules and
  beside a DLP rule's block, warn or hold. A journal whose scope chooses
  nobody takes only what rules send it.
- The report lists recipients a rule added or redirected to under
  "Added by rule", by rule name.
- A rule's route is cleared between messages in one SMTP session, with the
  new journal marks; a second message used to keep the first one's route.

tests/src/system/journal.rs: destination validation, a rule-only journal
fed by a rule that also adds a recipient, an unreachable archive's report
kept in the built-in journal with the failure counted, a report delivered
to an archive here and not journaled itself.

crates/smtp/src/inbound/session.rs

@@ -494,6 +494,10 @@ impl<T: AsyncWrite + AsyncRead + Unpin> Session<T> {
         self.data.delivery_by = 0;
         self.data.future_release = 0;
         self.data.rcpt_oks = 0;
+        // inbuxa: what mail flow rules decided was for the last message only
+        self.data.mailflow_queue = None;
+        self.data.journal_marks.clear();
+        self.data.journal_added.clear();
     }
 
     pub fn reset_tls(&mut self) {