docs: disa-stig hardening guide

[louiseschmidtgen]

Description

This PR updates the disa-stig instructions by including a disa-stig hardening page with the bootstrap/join templates as well as updates to the disa-stig assessment page.

Checklist

• PR title formatted as type: title
• Covered by unit tests
• Covered by integration tests
• Documentation updated
• CLA signed
• Backport label added if necessary

[nhennigan]

It is clear a lot of effort has gone into this, thanks Louise! I like the separation of the guides. I feel they were blurring the lines a bit between their purposes. I have been playing around with a few different versions of how to present the docs and this is what I have come up with (and how that relates to this PR):

snap 
|- how-to 
     |- install 
          |- how to install in FIPS mode / FIPS enabled CK8s
          |- how to install DISA STIG compliant (this would be your disa-stig-hardening)
     |- security 
          |- how to harden your cluster (basically the same as now but updated with latest from the playbook)
          |- how to assess CIS (this would just be kube-bench instructions)
|- reference
     |- CIS (all the CIS recommendations)
     |- DISA STIGs (All stigs - your disa-stig-assessment)
     |- security (update the links)
|- explanation 
     |- security (make this one page with disa stig and fips included)

How do you feel about this proposed layout? There would need to be a bit of rework of disa-stig-assessment to make it an install how to guide but I think the work you have done here is a massive help. The assumption would be that:

• you would have DISA STIG compliance achieved with the install guide (both host and k8s) so you won't really need a how to guide to disa stig the cluster (please tell me if Im wrong here)
• you can go to the reference if you need any specific steps audited
• you can apply the hardening guide after any install -> after this you will be CIS compliant and DISA STIG k8s only compliant

[rapour]

Thorough work @louiseschmidtgen, thanks, left a couple of comments

[rapour]

Great work @louiseschmidtgen