Include username in email headers (go-gitea#28981)

Emails from Gitea comments do not contain the username of the commenter
anywhere, only their display name, so it is not possible to verify who
made a comment from the email itself:

	From: "Alice" <email@gitea>
	X-Gitea-Sender: Alice
	X-Gitea-Recipient: Bob
	X-GitHub-Sender: Alice
	X-GitHub-Recipient: Bob

	This comment looks like it's from @alice.

The X-Gitea/X-GitHub headers also use display names, which is not very
reliable for filtering, and inconsistent with GitHub's behavior:

	X-GitHub-Sender: lunny
	X-GitHub-Recipient: gwymor

This change includes both the display name and username in the From
header, and switches the other headers from display name to username:

	From: "Alice (@fakeAlice)" <email@gitea>
	X-Gitea-Sender: fakealice
	X-Gitea-Recipient: bob
	X-GitHub-Sender: fakealice
	X-GitHub-Recipient: bob

	This comment looks like it's from @alice.

models/user/user.go

@@ -443,6 +443,17 @@ func (u *User) GetDisplayName() string {
 	return u.Name
 }
 
+// GetCompleteName returns the the full name and username in the form of
+// "Full Name (@username)" if full name is not empty, otherwise it returns
+// "@username".
+func (u *User) GetCompleteName() string {
+	trimmedFullName := strings.TrimSpace(u.FullName)
+	if len(trimmedFullName) > 0 {
+		return fmt.Sprintf("%s (@%s)", trimmedFullName, u.Name)
+	}
+	return fmt.Sprintf("@%s", u.Name)
+}
+
 func gitSafeName(name string) string {
 	return strings.TrimSpace(strings.NewReplacer("\n", "", "<", "", ">", "").Replace(name))
 }

services/mailer/mail.go

@@ -310,7 +310,13 @@ func composeIssueCommentMessages(ctx *mailCommentContext, lang string, recipient
 
 	msgs := make([]*Message, 0, len(recipients))
 	for _, recipient := range recipients {
-		msg := NewMessageFrom(recipient.Email, ctx.Doer.DisplayName(), setting.MailService.FromEmail, subject, mailBody.String())
+		msg := NewMessageFrom(
+			recipient.Email,
+			ctx.Doer.GetCompleteName(),
+			setting.MailService.FromEmail,
+			subject,
+			mailBody.String(),
+		)
 		msg.Info = fmt.Sprintf("Subject: %s, %s", subject, info)
 
 		msg.SetHeader("Message-ID", msgID)
@@ -394,8 +400,8 @@ func generateAdditionalHeaders(ctx *mailCommentContext, reason string, recipient
 
 		"X-Mailer":                  "Gitea",
 		"X-Gitea-Reason":            reason,
-		"X-Gitea-Sender":            ctx.Doer.DisplayName(),
-		"X-Gitea-Recipient":         recipient.DisplayName(),
+		"X-Gitea-Sender":            ctx.Doer.Name,
+		"X-Gitea-Recipient":         recipient.Name,
 		"X-Gitea-Recipient-Address": recipient.Email,
 		"X-Gitea-Repository":        repo.Name,
 		"X-Gitea-Repository-Path":   repo.FullName(),
@@ -404,8 +410,8 @@ func generateAdditionalHeaders(ctx *mailCommentContext, reason string, recipient
 		"X-Gitea-Issue-Link":        ctx.Issue.HTMLURL(),
 
 		"X-GitHub-Reason":            reason,
-		"X-GitHub-Sender":            ctx.Doer.DisplayName(),
-		"X-GitHub-Recipient":         recipient.DisplayName(),
+		"X-GitHub-Sender":            ctx.Doer.Name,
+		"X-GitHub-Recipient":         recipient.Name,
 		"X-GitHub-Recipient-Address": recipient.Email,
 
 		"X-GitLab-NotificationReason": reason,

services/mailer/mail_test.go

@@ -239,16 +239,16 @@ func TestGenerateAdditionalHeaders(t *testing.T) {
 	doer, _, issue, _ := prepareMailerTest(t)
 
 	ctx := &mailCommentContext{Context: context.TODO() /* TODO: use a correct context */, Issue: issue, Doer: doer}
-	recipient := &user_model.User{Name: "Test", Email: "test@gitea.com"}
+	recipient := &user_model.User{Name: "test", Email: "test@gitea.com"}
 
 	headers := generateAdditionalHeaders(ctx, "dummy-reason", recipient)
 
 	expected := map[string]string{
 		"List-ID":                   "user2/repo1 <repo1.user2.localhost>",
 		"List-Archive":              "<https://try.gitea.io/user2/repo1>",
 		"X-Gitea-Reason":            "dummy-reason",
-		"X-Gitea-Sender":            "< U<se>r Tw<o > ><",
-		"X-Gitea-Recipient":         "Test",
+		"X-Gitea-Sender":            "user2",
+		"X-Gitea-Recipient":         "test",
 		"X-Gitea-Recipient-Address": "test@gitea.com",
 		"X-Gitea-Repository":        "repo1",
 		"X-Gitea-Repository-Path":   "user2/repo1",