Write reference guide for using StackStorm in air-gapped environments

[LindsayHill]

StackStorm can be used in air-gapped environments (those where there is no direct or proxied Internet connection between the StackStorm server and the Internet).

Information for doing this is scattered in various places. We should provide a reference guide that pulls this together. Can still link to the other locations where it is.

Target audience is a smart sysadmin who knows the site procedures. It is not a "For Dummies" guide. Those people who really need air-gapped installs should know what they're doing, and why.

[arm4b]

As many of us noted before https://github.com/StackStorm/discussions/issues/260#issuecomment-332637492 ideally is to have Virtualbox/Vagrant VM image deployed to Vagrant cloud, similar to Docker hub.

So users could download beforehand fully pre-packed image artifact, carry to isolated server and just mount/start StackStorm it in their environment with 1 command.

Additionally, it will help our users to evaluate StackStorm really quick without a need to pre-install everything. Just:

vagrant init stackstorm/stackstorm
vagrant up

which will download respective image from https://app.vagrantup.com/boxes/search

---

While you're talking about the different approach here, I think it still worth mentioning boxes which will solve the problem in more easy way instead of going nuts with deb/rpm and configuration nightmare in internet-isolated systems.

[LindsayHill]

There's two different use-cases here:

1/ People that have air-gapped systems for policy or technical reasons, and just need an easy way of installing ST2 in those environments.
2/ People that are genuinely serious about security. They have air-gapped systems for strong technical & security reasons. They know why they're doing it, and they know the implications.

The first use-case is addressed by a virtual appliance type model, whether that be some form of OVA, Vagrant box, or something else. Conveniently, that model is also useful for those people who are not air-gapped, but want the convenience & repeatability of a single download, vs downloading lots of dependencies. It is definitely something we should pursue, but it will take a while to get something that fully addresses requirements there (eval is easy; ongoing maintenance and upgrades are hard).

The second use-case will not be addressed by a virtual appliance model. They will never be comfortable with the security implications of running a black box virtual appliance, and will want a higher level of control. We already support this type of deployment, we just don't make it particularly easy to figure out all the things required to do that. So for this specific issue, we should pull that information together a bit better, so smart sysadmins can see the steps they'll need to go through to do this, and things they'll need to take into consideration.