fix(email): use 'PostGuard' as sender display when no name is disclosed

When the signer discloses no name, the recipient email now reads
'PostGuard sent you files' instead of showing the raw sender email.
Also drop 'via PostGuard' from the subject — it would be redundant when
the sender is already 'PostGuard', and is cleaner for named senders too.

Renames the two tests that previously asserted the email fallback.

Author: rubenhensen

src/email.rs

@@ -136,7 +136,7 @@ struct MailStrings<'a> {
 }
 
 const NL_STRINGS: MailStrings = MailStrings {
-    subject_str: "heeft je een bestand gestuurd via PostGuard",
+    subject_str: "heeft je bestanden gestuurd",
     sender_str: "heeft je bestanden gestuurd",
     expires_str: "Verloopt op",
     download_str: "Download jouw bestanden",
@@ -148,7 +148,7 @@ const NL_STRINGS: MailStrings = MailStrings {
 };
 
 const EN_STRINGS: MailStrings = MailStrings {
-    subject_str: "sent you files via PostGuard",
+    subject_str: "sent you files",
     sender_str: "sent you files",
     expires_str: "Expires on",
     download_str: "Download your files",
@@ -221,11 +221,10 @@ fn build_body(html: String, text: String) -> Result<MultiPart, Box<dyn std::erro
 }
 
 /// Resolve the display string and remaining attribute pills for the
-/// sender. When the signer disclosed their full name, the name takes the
-/// place of the bare email everywhere it would otherwise appear in the
-/// body, and is removed from the attribute pill list so it doesn't render
-/// twice. An empty disclosed value is treated as not disclosed, so we
-/// fall through to the email instead of rendering a blank.
+/// sender. When the signer disclosed a name it is used as the display;
+/// the name attribute is removed from the pill list so it doesn't render
+/// twice. An empty disclosed value is treated as not disclosed. When no
+/// name is available the display falls back to "PostGuard".
 fn sender_display(state: &FileState) -> (String, Vec<(String, String)>) {
     let mut attrs = state.sender_attributes.clone();
 
@@ -239,9 +238,7 @@ fn sender_display(state: &FileState) -> (String, Vec<(String, String)>) {
         //    driving licence (postguard#239 follow-up).
         .or_else(|| take_firstname_lastname_pair(&mut attrs));
 
-    let display = name
-        .or_else(|| state.sender.clone())
-        .unwrap_or_else(|| "Someone".to_string());
+    let display = name.unwrap_or_else(|| "PostGuard".to_string());
     (display, attrs)
 }
 
@@ -581,14 +578,14 @@ mod tests {
             String::new(),
         )]);
         let (display, _) = sender_display(&state);
-        assert_eq!(display, "sender@example.com");
+        assert_eq!(display, "PostGuard");
     }
 
     #[test]
-    fn sender_display_falls_back_to_email_when_no_name_disclosed() {
+    fn sender_display_falls_back_to_postguard_when_no_name_disclosed() {
         let state = filestate_with_attrs(vec![("orgName".to_owned(), "Acme".to_owned())]);
         let (display, remaining) = sender_display(&state);
-        assert_eq!(display, "sender@example.com");
+        assert_eq!(display, "PostGuard");
         assert_eq!(remaining, vec![("orgName".to_owned(), "Acme".to_owned())]);
     }
 
@@ -686,7 +683,7 @@ mod tests {
         // No lastName → no concatenation; the orphan firstName stays as a
         // pill so the recipient at least sees it instead of having it
         // silently dropped.
-        assert_eq!(display, "sender@example.com");
+        assert_eq!(display, "PostGuard");
         assert_eq!(
             remaining,
             vec![(
@@ -709,15 +706,15 @@ mod tests {
             ),
         ]);
         let (display, _) = sender_display(&state);
-        assert_eq!(display, "sender@example.com");
+        assert_eq!(display, "PostGuard");
     }
 
     #[test]
-    fn sender_display_uses_someone_when_no_sender_and_no_name() {
+    fn sender_display_uses_postguard_when_no_name_disclosed() {
         let mut state = filestate_with_attrs(vec![]);
         state.sender = None;
         let (display, remaining) = sender_display(&state);
-        assert_eq!(display, "Someone");
+        assert_eq!(display, "PostGuard");
         assert!(remaining.is_empty());
     }