SPIKE: Migrate the XSLT implementation into its own repository

[david-waltermire]

User Story:

As a user of Metaschema, I need a clean separation between the core Metaschema artifacts (i.e., schemas, specification, generalized tests) and the XSLT-based Metaschema implementation that coexists in this repository.

As a maintainer of either the core Metaschema artifacts or the XSLT implementation, I need a way to independently maintain and version each effort.

Goals:

Ensure that dependent projects are not impacted by these changes (i.e., ensure pinning to a commit is usable).

The artifacts that will remain in this repository are:

• Metaschema XML schema and JSON and XML data type schemas.
• Website documentation related to core use of Metaschema and its specification.
• Generalized unit tests for core Metaschema features.

Actions to take:

• Create a repository fork of this repo that will be used for maintenance of the XSLT implementation.
  • Setup CI/CD in this repository.
  • Figure out how to use the Metaschema repo as a dependency (i.e., tagging, submodule).
• Remove XSLT code and related files from this repo.

Dependencies:

None.

Acceptance Criteria

• The XSLT Metaschema implementation has been relocated
• All XSLT Metaschema implementation code is removed.
• Generalized tests are usable by Metaschema implementations.
• 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.

[wendellpiez]

New repository is here: https://github.com/usnistgov/metaschema-xslt

[nikitawootten-nist]

@wendellpiez and I have set up the fork, and deleted the existing website infrastructure. We have created a few issues on the new project's board, summarized in this milestone.

For now we will be working out of the "develop" branch, and will set up new branching infrastructure when it is all ready.

[nikitawootten-nist]

@david-waltermire-nist on a more administrative note I created the ITL-Metaschema team and updated the new repo's CODEOWNERS to follow. We can create subteams as you see fit.

[wendellpiez]

New repo work in progress is here: https://github.com/wendellpiez/metaschema-xslt/tree/issue2-migration-fixup behind PR #3

A branch of this repo with XSLT implementation removed, with PR, is coming RSN.

[nikitawootten-nist]

@david-waltermire-nist this issue should likely be transferred back upstream

[wendellpiez]

PR #3 is now merged! addressing half this Issue.

Note top level of new repo is currently develop, not `main'.

[wendellpiez]

More work needs to be done on integrating testing, but that is better done with specific requirements in view, on new Issues.