fix warnings with Scala 3.4. avoid `private[this]`

[xuwei-k]

Pull Request Checklist

• [x] Have you read How to write the perfect pull request?
• [x] Have you read through the contributor guidelines?
• [x] Have you referenced any issues you're fixing using commit message keywords?
• [x] Have you added copyright headers to new files?
• [x] Have you checked that both Scala and Java APIs are updated?
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• [x] Have you added tests for any changed functionality?

Helpful things

Fixes

Purpose

fix warnings. use private instead of private[this] in routes-compiler generate code.

Background Context

• https://github.com/lampepfl/dotty/pull/18819
• https://docs.scala-lang.org/scala3/reference/dropped-features/this-qualifier.html

References

[ahjohannessen]

@mkurz Can this be merged?

[mkurz]

@Mergifyio backport 2.9.x

[mergify[bot]]

backport 2.9.x

✅ Backports have been created

• #12364 [2.9.x] fix warnings with Scala 3.4. avoid private[this] (backport #12284) by @xuwei-k has been created for branch 2.9.x

[ahjohannessen]

@mkurz Would be nice with a minor release with this :)

[mkurz]

@mkurz Would be nice with a minor release with this :)

This will be in the next patch release even, however I don't have a rush just because of this pull request, because we do not officially support non-LTS Scala releases. Just be patient :wink: