Prepare Allowed Values from OSCAL and FedRAMP Before Runtime

[mike-stern]

As a developer using the FedRAMP Validations, in order to read important values needed for validation at build time without needing to change or understand the validations' source code , I want the FedRAMP Validations to process values from OSCAL source code and FedRAMP values on the fly.

Context:

This is the spike to research the viability of o:allowed-values from multiple sources: investigate programmatically generating Schematron from OSCAL Metaschema and FedRAMP extensions

Pre-conditions:

Acceptance Criteria:

• [ ] understand how their future vision of OSCAL metaschema and FedRAMP extensions may enable
• [ ] Update mechanism for reading FedRAMP Extension data for o:allowed-values
• [ ] Document strategy for handling OSCAL Metaschema data for o:allowed-values that will need to be used to match
• [ ] Update mechanism for reading OSCAL Metaschema data for o:allowed-values

Definition of Done:

[sstatz]

Wait for review. Needs more discussion.

[sstatz]

Need to coordinate with NIST OSCAL developers.