Create ADR for rev 4/5 tagging approach (source: 18F/fedramp-automation: 615)

[danielnaab]

Original issue: 18F#615

Extended Description
As a FedRAMP rule writer, I would like to be able to tag Schematron rules to their corresponding NIST RMF revision, and have them evaluated in the appropriate context.

Acceptance Criteria

• Architectural decision record written with approach
• Optionally, one or more initial rules tagged with this approach
• Optionally, integrated into UI

Definition of Done

• Acceptance criteria met
• Unit test coverage of our code > 95%
• Automated code quality checks passed
• Security reviewed and reported
• Reviewed against plain language guidelines
• Code must be self-documenting
• No local tech debt
• Load/performance tests passed – needs to be created/automated
• Documentation updated
• Architectural Decision Record completed as necessary for significant design choices
• PR reviewed & approved
• Source code merged