Add "is_substring" variable to grub2_bootloader_argument template

[Xeicker]

Description:

• Add the is_substring variable to grub2_bootloader_argument template. And set it to False as default
  • This argument only applies to OVAL, as a robust remediation could be tricky to handle any case
• Set is_substring to true in grub2_slub_debug_argument rule for OL8

Rationale:

• With OL8 STIG v1R10 update the requirement OL08-00-010423 allows P to be a sub string of the configuration

If "slub_debug" does not contain "P", is missing, or is commented out, this is a finding.

Note: @ComplianceAsCode/red-hatters This could also be applicable to RHEL8, please let me know if I should make the update for RHEL8 also

Review Hints:

• Added automatus tests to validate this change

[github-actions]

Start a new ephemeral environment with changes proposed in this pull request:

rhel8 (from CTF) Environment (using Fedora as testing environment)

Fedora Testing Environment

Oracle Linux 8 Environment

[github-actions]

🤖 A k8s content image for this PR is available at:
ghcr.io/complianceascode/k8scontent:12308
This image was built from commit: d7f142c

Click here to see how to deploy it

If you alread have Compliance Operator deployed:
utils/build_ds_container.py -i ghcr.io/complianceascode/k8scontent:12308

Otherwise deploy the content and operator together by checking out ComplianceAsCode/compliance-operator and:
CONTENT_IMAGE=ghcr.io/complianceascode/k8scontent:12308 make deploy-local

[codeclimate]

Code Climate has analyzed commit d7f142c and detected 0 issues on this pull request.

The test coverage on the diff in this pull request is 100.0% (50% is the threshold).

This pull request will bring the total coverage in the repository to 59.4% (0.0% change).

View more on Code Climate.

[jan-cerny]

I have extended this patch to RHEL 9 and then tried to run the test scenarios with it.