Implement data processing policy for common controls

[mitchelbaker-cisa]

🗣 Description

Implement rego for "Data SHALL be processed in the region selected for data at rest." common controls policy 15.2. This can be found under Data -> Compliance -> Data Regions -> Data Processing in the admin console.

💭 Motivation and context

Closes #444

🧪 Testing

Tested manually with the setting checked/unchecked for only root OU, overridden for sub-level OUs, only groups, and a combination of OUs and groups.

Run unit tests with

cd ./Testing
python ./run_unit_tests.py -b commoncontrols

✅ Pre-approval checklist

• This PR has an informative and human-readable title.
• Changes are limited to a single goal - eschew scope creep!
• If applicable, All future TODOs are captured in issues, which are referenced in the PR description.
• The relevant issues PR resolves are linked preferably via closing keywords.
• All relevant type-of-change labels have been added.
• I have read and agree to the CONTRIBUTING.md document.
• These code changes follow cisagov code standards.
• All relevant repo and/or project documentation has been updated to reflect the changes in this PR.
• Tests have been added and/or modified to cover the changes in this PR.
• All new and existing tests pass.
• Confirm default setting.

✅ Pre-merge Checklist

• This PR has been smoke tested to ensure main is in a functional state when this PR is merged.
• Squash all commits into one PR level commit using the Squash and merge button.

✅ Post-merge Checklist

• Delete the branch to clean up.
• Close issues resolved by this PR if the closing keywords did not activate.

[buidav]

• Confirm default setting. Do we want to confirm it in this pull request or a later time?

[mitchelbaker-cisa]

Default setting is set to unchecked, commit added to fix. Merging into main.