Prevent staging environments from getting indexed by search engines

Staging environments are often insufficiently protected, meaning they can be accessed by both search engines (sometimes even indexed) and third-parties.

There's no need for that, it's easy to lock staging environments down. I scored all methods that can help with this for: - User-friendliness: the degree to which the method doesn’t add extra inconvenience. - Third-party access: the degree to which the method prevents third parties from accessing an environment. - SEO-friendliness: the degree to which the method keeps search engines from indexing an environment. - Monitoring-friendliness: the degree to which the method lets you monitor the protected environments for SEO purposes. - Risk of human error: the degree to which the method may lead to human errors, impacting SEO.

I hope this is useful for the HN community, and that it prevents a few more staging environments from getting indexed/accessed.