inbound-antispam-panel: inbound journal milter on port 25

Step 3/12 of docs/plans/inbound-antispam-panel.md.

The panel serves a second milter while the inbound relay is on
(internal/milter/inbound.go, socket INBOUND_JOURNAL_MILTER_SOCKET,
default /run/selfpost/inbound-journal.sock). build/postfix-config.sh
puts it last on port 25, after the optional antispam milter, with
default_action=accept; postfix-wrapper.sh waits for its socket. At
end-of-message it writes one inbound_spam_log row per recipient at an
inbound domain - other port-25 recipients (DMARC report addresses) get
none - and always accepts. With a filter attached it reads the verdict
from X-Rspamd-Action and X-Spamd-Result (action, score, up to six
weighted symbols, only what the patterns recognise, 255 bytes); without
one those headers are the sender's and are not read. The plan named
X-Rspamd-Score, which rspamd does not have.

The antispam compose fragment mounts rspamd/milter_headers.conf into
the sidecar so that it adds the two headers (checked in rspamd 3.11:
both routines exist and remove a sender's own headers of those names).

Store: InsertInboundSpam, IsInboundDomain.

Checked on the test server, uncommitted tree: go vet ./... ok,
go test ./... ok (22 packages), make e2e ok - the relayed message of
inbound_relay_delivers_and_refuses has its journal row (accept by
selfpost) and the DMARC report sent through the same listener has none.

Not yet seen in a real run: a verdict written by rspamd reaching this
milter. The e2e stand has no filter, and the test server's only inbound
domain has no upstream, so it accepts no mail.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/store/inboundspam_test.go

@@ -0,0 +1,61 @@
+package store
+
+import (
+	"testing"
+	"time"
+)
+
+func TestInsertInboundSpam(t *testing.T) {
+	st := openTestStore(t)
+	e := InboundSpamEntry{
+		InboundDomain: "in.example.com", ClientIP: "203.0.113.7",
+		From: "sender@example.net", To: "a@in.example.com", Subject: "Hello",
+		Decision: SpamDecisionAccept, Engine: SpamEngineRspamd, Detail: "no action, score 0.10 / 15.00",
+	}
+	if err := st.InsertInboundSpam(e); err != nil {
+		t.Fatalf("InsertInboundSpam: %v", err)
+	}
+	var got InboundSpamEntry
+	var created string
+	err := st.db.QueryRow(
+		"SELECT inbound_domain, client_ip, from_addr, to_addr, subject, decision, engine, detail, created_at FROM inbound_spam_log",
+	).Scan(&got.InboundDomain, &got.ClientIP, &got.From, &got.To, &got.Subject, &got.Decision, &got.Engine, &got.Detail, &created)
+	if err != nil {
+		t.Fatalf("read back: %v", err)
+	}
+	if got != e {
+		t.Errorf("row = %+v\nwant  %+v", got, e)
+	}
+	if at, err := time.Parse(time.RFC3339, created); err != nil || time.Since(at) > time.Minute {
+		t.Errorf("created_at = %q (%v)", created, err)
+	}
+
+	// Every decision and engine the code names is one the table takes.
+	for _, d := range []string{SpamDecisionAccept, SpamDecisionReject, SpamDecisionTempfail, SpamDecisionQuarantine} {
+		for _, eng := range []string{SpamEngineRspamd, SpamEnginePostfix, SpamEngineSelfPost} {
+			e.Decision, e.Engine = d, eng
+			if err := st.InsertInboundSpam(e); err != nil {
+				t.Errorf("decision %s by %s: %v", d, eng, err)
+			}
+		}
+	}
+	e.Decision = "bounce"
+	if err := st.InsertInboundSpam(e); err == nil {
+		t.Error("an unknown decision was stored")
+	}
+}
+
+func TestIsInboundDomain(t *testing.T) {
+	st := openTestStore(t)
+	if _, err := st.AddInboundDomain("in.example.com"); err != nil {
+		t.Fatalf("AddInboundDomain: %v", err)
+	}
+	for name, want := range map[string]bool{
+		"in.example.com": true, "IN.Example.COM": true,
+		"example.com": false, "": false, "other.example.com": false,
+	} {
+		if got, err := st.IsInboundDomain(name); err != nil || got != want {
+			t.Errorf("IsInboundDomain(%q) = %v, %v; want %v", name, got, err, want)
+		}
+	}
+}