Schema validation for Metaschema instances under CI/CD

[wendellpiez]

User Story:

Many learners' errors (and worse) could be prevented from propagating accidentally if we were to provide PR-time validation of Metaschema instances, i.e. any and all metaschemas in the repo (mainly testing) that must run for tests to run.

Goals:

We need these capabilities from the command line and in CI/CD:

• Validate a metaschema against the current Metaschema XSD
• Validate a metaschema against any/all available/appropriate Schematrons
• Provide appropriate configurability
• Set up to run under make and CI/CD (under smoke-test or other appropriate target)

A configurable XProc step could be a nice way to do this, with a little script for invocation.

An example of a metaschema instance to be validated is in the testing folder.

Having done this for one testing metaschema we can then proceed to validate any/all.

Dependencies:

None known.

In a branch now being staged (not yet merged) there is relevant work: see https://github.com/usnistgov/metaschema-xslt/pull/108

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.}

[wendellpiez]

Now being addressed in the working branch behind #108.