Add support for Application Settings API attribute `pages_unique_domain_default_enabled`. API Docs: https://docs.gitlab.com/api/settings/ ## Implementation Guide - Follow the `CONTRIBUTING.md` guide for setting up your local development environment. - Clone the community fork of this project. - In `settings.go`, add a new bool field called `PagesUniqueDomainDefaultEnabled` to the `Settings` and `UpdateSettingsOptions` structs.