[kotlin-client] ALL: Prevent HTML-escaping of operation parameter defaults

[okarmazin]

Fixes #22505

Kotlin client API templates now pass through enum defaults of operation parameters as raw values. Prevents incorrect HTML-escaping of Kotlin backticks if the default enum constant is a reserved Kotlin word.

Old output:

fun documentDownload(disposition: DispositionDocumentDownload? = DispositionDocumentDownload.`inline`) : java.io.File

Fixed output:

fun documentDownload(disposition: DispositionDocumentDownload? = DispositionDocumentDownload.`inline`) : java.io.File

New tests should cover all present and future clients that generate enum classes.

This PR builds upon #22504 and I'll rebase when that gets merged.

The GitHub diff viewer is not very good. This is a single-character change in multiple templates that replaces {{enumDefaultValue}} with {{&enumDefaultValue}}

PR checklist

• [X] Read the contribution guidelines.
• [X] Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
• [X] Run the following to build the project and update samples:

  ./mvnw clean package || exit
  ./bin/generate-samples.sh ./bin/configs/*.yaml || exit
  ./bin/utils/export_docs_generators.sh || exit
  

  (For Windows users, please run the script in WSL) Commit all changed files. This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master. These must match the expectations made by your contribution. You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*. IMPORTANT: Do NOT purge/delete any folders/files (e.g. tests) when regenerating the samples as manually written tests may be removed.
• [X] File the PR against the correct branch: master (upcoming 7.x.0 minor release - breaking changes with fallbacks), 8.0.x (breaking changes without fallbacks)
• [X] If your PR solves a reported issue, reference it using GitHub's linking syntax (e.g., having "fixes #123" present in the PR description)
• [ ] If your PR is targeting a particular programming language, @mention the technical committee members, so they are more likely to review the pull request.

[Picazsoo]

Hello @okarmazin, I presume the same issue is present also in other kotlin generators?

[okarmazin]

Hello @okarmazin, I presume the same issue is present also in other kotlin generators?

I don't know, but the only usages of enumDefaultValue, which is what this PR fixes, come from the kotlin-client folder. I haven't looked at how server generators handle default values, or if they even do.

[Picazsoo]

Just checked - this seems to work correctly in kotlin-spring generator.