Resource hints are currently stored as a delimited string in the variables system. Per "pending functionality" in the project description, resource hints require individual configuration to support the crossorigin and as attributes for comprehensive support of all resource hints requirements/features.
Pivot to a new resource hint entity type and leverage the entity facilities to manage configurations for a resource hint in an individual basis, and refactor any/all current functionality as necessary.
Yes. Entity CRUD using the base entity management forms available in the entity ecosystem.
N/A. See ✨ Module hook to alter resource hint array Closed: won't fix
Yes. New resource hints entity.
Closed: won't fix
2.0
Code
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It's likely this issue predates Contrib.social: some issue and comment data are missing.
There isn't any current interest in working on the Drupal 7 branch. Since D7 is end of life in a few months, I am going to close this as won't fix. Please feel free to open it back up if you would like to work on it.