Description

This adds a new historyRestoreAsHxRequest config item to disable a breaking change made in #2013 where now we return HX-Request response header when requesting full page responses which causes many issues for users following our documentation that clearly states to use this response header for returning partial fragments. When returning partials based on this response header without knowing to also check and vary your cache on the HX-History-Restore-Request header your app will sometimes display the wrong result.

This config item is set to default to true to keep the breaking change in place for now so users relying on this behavior will not be impacted and users who need to return partial responses can disable this config as needed.

Corresponding issue:
#3037

Testing

Updated tests to test both states of the config value

Checklist

• I have read the contribution guidelines
• I have targeted this PR against the correct branch (master for website changes, dev for
  source changes)
• This is either a bugfix, a documentation update, or a new feature that has been explicitly
  approved via an issue
• I ran the test suite locally (npm run test) and verified that it succeeded