TF-4195 Implement add a Label to an email

lib/features/thread/domain/extensions/presentation_email_map_extension.dart

@@ -0,0 +1,30 @@
+import 'package:jmap_dart_client/jmap/mail/email/email.dart';
+import 'package:jmap_dart_client/jmap/mail/email/keyword_identifier.dart';
+import 'package:model/email/presentation_email.dart';
+import 'package:tmail_ui_user/features/email/presentation/extensions/presentation_email_extension.dart';
+
+extension PresentationEmailMapExtension on Map<EmailId, PresentationEmail?> {
+  Map<EmailId, PresentationEmail?> addEmailKeywordById({
+    required EmailId emailId,
+    required KeyWordIdentifier keyword,
+  }) {
+    return map((id, email) {
+      if (id != emailId || email == null) {
+        return MapEntry(id, email);
+      }
+      return MapEntry(id, email.addKeyword(keyword));
+    });
+  }
+
+  Map<EmailId, PresentationEmail?> removeEmailKeywordById({
+    required EmailId emailId,
+    required KeyWordIdentifier keyword,
+  }) {
+    return map((id, email) {
+      if (id != emailId || email == null) {
+        return MapEntry(id, email);
+      }
+      return MapEntry(id, email.removeKeyword(keyword));
+    });
+  }
+}