fix(imap): record HIGHESTMODSEQ from a STATUS response

lib/src/private/imap/status_parser.dart

@@ -48,6 +48,9 @@ class StatusParser extends ResponseParser<Mailbox> {
           case 'UNSEEN':
             box.messagesUnseen = value;
             break;
+          case 'HIGHESTMODSEQ':
+            box.highestModSequence = value;
+            break;
           default:
             print(
               'unexpected STATUS: $entry=${listEntries[i + 1]}\nin $details',

test/src/imap/status_parser_test.dart

@@ -3,6 +3,7 @@ import 'package:enough_mail/src/private/imap/all_parsers.dart';
 import 'package:enough_mail/src/private/imap/imap_response.dart';
 import 'package:enough_mail/src/private/imap/imap_response_line.dart';
 import 'package:test/test.dart';
+
 // cSpell:disable
 
 void main() {
@@ -58,4 +59,26 @@ void main() {
     expect(processed, true);
     expect(box.messagesExists, 2);
   });
+
+  test('Status with HIGHESTMODSEQ', () {
+    // A CONDSTORE server includes HIGHESTMODSEQ when asked for it (RFC 7162
+    // section 3.1.6). It used to fall into the default branch and be printed
+    // as unexpected instead of being recorded on the mailbox.
+    const responseText =
+        'STATUS "INBOX" (MESSAGES 231 UNSEEN 5 HIGHESTMODSEQ 7011231777)';
+    final details = ImapResponse()..add(ImapResponseLine(responseText));
+    final box = Mailbox(
+      encodedName: 'INBOX',
+      encodedPath: 'INBOX',
+      flags: [MailboxFlag.inbox],
+      pathSeparator: '/',
+    );
+    final parser = StatusParser(box);
+    final response = Response<Mailbox>()..status = ResponseStatus.ok;
+    final processed = parser.parseUntagged(details, response);
+    expect(processed, true);
+    expect(box.messagesExists, 231);
+    expect(box.messagesUnseen, 5);
+    expect(box.highestModSequence, 7011231777);
+  });
 }