FED-2138 Fix createContext typing

[greglittlefield-wf]

Motivation

The current typing for createContext is incorrect/unsound.

Context<TValue> createContext<TValue>([TValue? defaultValue, int Function(TValue?, TValue?)? calculateChangedBits]) {...}

But if you don't provide a default value, the value will be null, which isn't a TValue when TValue is a non-nullable type. And also, it's possible to provide null even when TValue is non-nullable.

This typing problem is essentially the same as useRef, for which we had to create useRefInit (link), and deprecated the arg to useRef. That way, we won't have to break createContext, and people passing the deprecated argument will get a deprecation hint telling them to move to the new one.

Changes

• Update createContext to always return contexts with nullable type, since we can't guarantee that a default value was provided
• Add createContext, which allows creation of contexts with non-nullable types, and required specifying a default value
• Doc comments
  • Update examples to default values, include a useContext example
  • Update links to point to new React docs
• Update tests, add test coverage for default values

Release Notes

Review

See CONTRIBUTING.md for more details on review types (+1 / QA +1 / +10) and code review process.

Please review:

QA Checklist

• Tests were updated and provide good coverage of the changeset and other affected code
• Manual testing was performed if needed
  • Steps from PR author:
    • CI passes
  • Anything falling under manual testing criteria outlined in CONTRIBUTING.md

Merge Checklist

While we perform many automated checks before auto-merging, some manual checks are needed:

• A Frontend Frameworks Design member has reviewed these changes
• There are no unaddressed comments - this check can be automated if reviewers use the "Request Changes" feature
• For release PRs - Version metadata in Rosie comment is correct

[aviary3-wk]

Security Insights

No security relevant content was detected by automated scans.

Action Items

• Review PR for security impact; comment "security review required" if needed or unsure
• Verify aviary.yaml coverage of security relevant code

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[aaronlademann-wf]

Just a typo and some confusing doc comments... otherwise I'm plus one @greglittlefield-wf

[aaronlademann-wf]

NICE

[greglittlefield-wf]

@aaronlademann-wf Good catches on the doc comments, addressed in 2bba27d!

[aaronlademann-wf]

+10

• Passing CI