[#1728] normalized mailer.Message recipient fields

tools/mailer/mailer.go

@@ -8,9 +8,9 @@ import (
 // Message defines a generic email message struct.
 type Message struct {
 	From        mail.Address
-	To          mail.Address
-	Bcc         []string
-	Cc          []string
+	To          []mail.Address
+	Bcc         []mail.Address
+	Cc          []mail.Address
 	Subject     string
 	HTML        string
 	Text        string
@@ -23,3 +23,21 @@ type Mailer interface {
 	// Send sends an email with the provided Message.
 	Send(message *Message) error
 }
+
+// addressesToStrings converts the provided address to a list of serialized RFC 5322 strings.
+//
+// To export only the email part of mail.Address, you can set withName to false.
+func addressesToStrings(addresses []mail.Address, withName bool) []string {
+	result := make([]string, len(addresses))
+
+	for i, addr := range addresses {
+		if withName && addr.Name != "" {
+			result[i] = addr.String()
+		} else {
+			// keep only the email part to avoid wrapping in angle-brackets
+			result[i] = addr.Address
+		}
+	}
+
+	return result
+}