Chart.js: New scriptable options context - breaking changes?

Documentation Is:

• Missing or needed
• Confusing
• Not Sure?

Please Explain in Detail…

The PR #7981 changed the structure of the scriptable options context.

Now, doing some tests applying a callback to backgroudColor to a dataset, the chart instance is missing.

Your Proposal for Changes

In my opinion, the context should contain always a reference to the chart in order to leave the coder to apply whatever logic he/she wants.

Furthermore I think this is a breaking change and it should be documented into migration guide.

Last but not least, the documentation is unclear because, if I have understood correct, the context can have different contents but you must specify well when the different types (chart, dataset, data, scale and tick) are used, for which options node