when generating Authentication-Results, put each method on a new line for better readability

message/authresults.go

@@ -66,6 +66,8 @@ func (h AuthResults) Header() string {
 	w := &HeaderWriter{}
 	w.Add("", "Authentication-Results:"+optComment(h.Comment)+" "+value(h.Hostname)+";")
 	for i, m := range h.Methods {
+		w.Newline()
+
 		tokens := []string{}
 		addf := func(format string, args ...any) {
 			s := fmt.Sprintf(format, args...)
@@ -86,10 +88,14 @@ func (h AuthResults) Header() string {
 			addf("%s.%s=%s%s", p.Type, p.Property, v, optComment(p.Comment))
 		}
 		for j, t := range tokens {
+			var sep string
+			if j > 0 {
+				sep = " "
+			}
 			if j == len(tokens)-1 && i < len(h.Methods)-1 {
 				t += ";"
 			}
-			w.Add(" ", t)
+			w.Add(sep, t)
 		}
 	}
 	return w.String()

message/authresults_test.go

@@ -19,7 +19,7 @@ func TestAuthResults(t *testing.T) {
 		},
 	}
 	s := authRes.Header()
-	const exp = "Authentication-Results: (xn--mx-lka.example) møx.example; dkim=pass\r\n\theader.d=møx.example (xn--mx-lka.example)\r\n"
+	const exp = "Authentication-Results: (xn--mx-lka.example) møx.example;\r\n\tdkim=pass header.d=møx.example (xn--mx-lka.example)\r\n"
 	if s != exp {
 		t.Fatalf("got %q, expected %q", s, exp)
 	}

message/headerwriter.go

@@ -59,6 +59,13 @@ func (w *HeaderWriter) AddWrap(buf []byte) {
 	}
 }
 
+// Newline starts a new line.
+func (w *HeaderWriter) Newline() {
+	w.b.WriteString("\r\n\t")
+	w.lineLen = 1
+	w.nonfirst = true
+}
+
 // String returns the header in string form, ending with \r\n.
 func (w *HeaderWriter) String() string {
 	return w.b.String() + "\r\n"