Add a datacenter resource.

[hdost]

The purpose of this is to allow for people running in a hybrid environment.

Relates #1409

Changes

Please provide a brief description of the changes here.

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Merge requirement checklist

• [x] CONTRIBUTING.md guidelines followed.
• [x] Change log entry added, according to the guidelines in When to add a changelog entry.
  • If your PR does not need a change log, start the PR title with [chore]
• [x] schema-next.yaml updated with changes to existing conventions.