Improve "dev.san99tiago.com" environment with private access

[san99tiago]

The main idea is to be able to test in a completely isolated/private way the CloudFront distribution and/or the route 53 record, so that it is only accesible by a pre-signed url or a custom approach (in this way, we can have a private environment that is not publicly distributed globally via CloudFront).

As this is not a top-tier highly secure website, it's not a mandatory thing to do, but it's a good development practice to include later on.