Update Metaschema Syntax Documentation to Refer to Token Types, Not IDs

[aj-stein-nist]

User Story:

As a NIST OSCAL developer, in order to properly understand JSON enhancement features, I would like to have clearer documentation about key, ID, and the appropriate Metaschema types.

Goals:

• Update the following section and additional relevant references on the syntax page.

To support this, flags used as addresses should be declared as type ID, providing "an extra layer of protection". On the JSON side, validating the uniqueness of these values (on same-named properties across document scope) remains TBD.

Dependencies:

{Describe any previous issues or related work that must be completed to start or complete this issue.}

Acceptance Criteria

• All website and readme documentation affected by the changes in this issue have been updated. Changes to the website can be made in the docs/content directory of your branch.
• A Pull Request (PR) is submitted that fully addresses the goals of this User Story. This issue is referenced in the PR.
• The CI-CD build process runs without any reported errors on the PR. This can be confirmed by reviewing that all checks have passed in the PR.

{The items above are general acceptance criteria for all User Stories. Please describe anything else that must be completed for this issue to be considered resolved.}

[aj-stein-nist]

Per discussion with team reorganization, I will move this Metaschema issue off the NIST OSCAL workboard.

[aj-stein-nist]

I recommend we include this for a release before or latest as a part of 1.0.0 release.

[david-waltermire]

Addressed by PR #329.