implement outgoing dmarc aggregate reporting

in smtpserver, we store dmarc evaluations (under the right conditions).
in dmarcdb, we periodically (hourly) send dmarc reports if there are
evaluations. for failed deliveries, we deliver the dsn quietly to a submailbox
of the postmaster mailbox.

this is on by default, but can be disabled in mox.conf.

testdata/dmarcdb/domains.conf

@@ -0,0 +1,28 @@
+Domains:
+	mox.example:
+		DKIM:
+			Selectors:
+				testsel:
+					PrivateKeyFile: testsel.rsakey.pkcs8.pem
+			Sign:
+				- testsel
+Accounts:
+	other:
+		Domain: mox.example
+		Destinations:
+			other@mox.example: nil
+	mjl:
+		MaxOutgoingMessagesPerDay: 30
+		MaxFirstTimeRecipientsPerDay: 10
+		Domain: mox.example
+		Destinations:
+			mjl@mox.example: nil
+			møx@mox.example: nil
+		RejectsMailbox: Rejects
+		JunkFilter:
+			Threshold: 0.95
+			Params:
+				Twograms: true
+				MaxPower: 0.1
+				TopWords: 10
+				IgnoreWords: 0.1

testdata/dmarcdb/mox.conf

@@ -0,0 +1,11 @@
+DataDir: data
+User: 1000
+LogLevel: trace
+Hostname: mail.mox.example
+Listeners:
+	local:
+		IPs:
+			- 0.0.0.0
+Postmaster:
+	Account: mjl
+	Mailbox: postmaster

testdata/dmarcdb/testsel.rsakey.pkcs8.pem

@@ -0,0 +1,30 @@
+-----BEGIN PRIVATE KEY-----
+Note: RSA private key for use with DKIM, generated by mox
+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+-----END PRIVATE KEY-----