With WordPress 4.7 the REST API is part of the core. At the moment everyone has read access to the REST API. As a result of that a potential intruder can retrieve a list of all user slugs via /wp-json/wp/v2/users. This plugin disables the REST API user endpoints to obscure the user slugs.
Contributions are more than welcome. Simply head over to Github and open an issue or a pull request.