mailer: Put the username in X-Forgejo-Sender and -Recipient

Following gitea#28981, set `X-Forgejo-Sender` and `X-Forgejo-Recipient`
to the username of the respective users, rather than their display name.
The username is more appropriate for these headers, for filtering
purposes. The display name is already included in the From header.

Signed-off-by: Gergely Nagy <forgejo@gergo.csillger.hu>

services/mailer/mail.go

@@ -415,8 +415,8 @@ func generateAdditionalHeaders(ctx *mailCommentContext, reason string, recipient
 		"X-Gitea-Issue-Link":        ctx.Issue.HTMLURL(),
 
 		"X-Forgejo-Reason":            reason,
-		"X-Forgejo-Sender":            ctx.Doer.DisplayName(),
-		"X-Forgejo-Recipient":         recipient.DisplayName(),
+		"X-Forgejo-Sender":            ctx.Doer.Name,
+		"X-Forgejo-Recipient":         recipient.Name,
 		"X-Forgejo-Recipient-Address": recipient.Email,
 		"X-Forgejo-Repository":        repo.Name,
 		"X-Forgejo-Repository-Path":   repo.FullName(),

services/mailer/mail_test.go

@@ -369,6 +369,8 @@ func TestGenerateAdditionalHeaders(t *testing.T) {
 		"X-Gitea-Repository-Link":   "https://try.gitea.io/user2/repo1",
 		"X-Gitea-Issue-ID":          "1",
 		"X-Gitea-Issue-Link":        "https://try.gitea.io/user2/repo1/issues/1",
+		"X-Forgejo-Sender":          "user2",
+		"X-Forgejo-Recipient":       "test",
 	}
 
 	for key, value := range expected {