Revisit using commit id as version for resource index JSON

[joverlee521]

Context

Currently we are using numbered revisions for the resource index JSON, e.g. resources/v1.json.gz.
This means devs have to be cognizant of when to bump the revision number and there's also potential for revision number clashes between WIP branches and PRs.

Past discussion floated the idea of using commit ids as the version of the resource index, but leaving this as future decision.