In back-matter, for a resource, the rlink/hash/@value is required, not optional

[aj-stein-gsa]

Hello per discussion and review of a user report around FedRAMP constraints and the oscal-cli in GSA/fedramp-automation#787, we determined that the documentation generation pipeline for the OSCAL-Reference model outlines and index of fields incorrectly indicates that the back-matter/resource/hash/@value is not [0 to 1] but rather 1. The processing of fhe json-value-key in the documentation is being incorrectly processed to be an optional field or flag in some way, but it is not.

https://github.com/usnistgov/OSCAL/blob/v1.1.2/src/metaschema/oscal_metadata_metaschema.xml#L930

https://pages.nist.gov/OSCAL-Reference/models/v1.1.2/complete/json-outline/

https://pages.nist.gov/OSCAL-Reference/models/v1.1.2/system-security-plan/json-reference/#/system-security-plan/back-matter/resources/rlinks/hashes/value

I am not sure what proper fix is needed in the metaschema-xslt pipeline per the sub-module version defined in the code infrastrcture here and called by generate_modeldoc.sh by the Makefile, to resolve this issue and how systemic it is, but I can help further troubleshoot and debug fixes accordingly.