fix(typescript-fetch): Use null as a value when the date value is nullable

[tikki100]

Currently, null is not used as a value for date values - even when the property is nullable. This means you're unable to construct a request with null. This PR fixes that.

PR checklist

• 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.
• Run the following to build the project and update samples:
  ./run-in-docker.sh generate -g typescript-fetch -o /gen/samples/client/petstore/typescript-fetch/builds/default-v3.0 -i modules/openapi-generator/src/test/resources/3_0/petstore-with-fake-endpoints-models-for-testing.yaml
  (For Windows users, please run the script in Git BASH)
  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.
• 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) (I think I've choosen correctly?)
• If your PR is targeting a particular programming language, @mention the technical committee members, so they are more likely to review the pull request.

Technical Committee

@TiFu (2017/07) @taxpon (2017/07) @sebastianhaas (2017/07) @kenisteward (2017/07) @Vrolijkx (2017/09) @macjohnny (2018/01) @topce (2018/10) @akehir (2019/07) @petejohansonxo (2019/11) @amakhrov (2020/02) @davidgamero (2022/03) @mkusaka (2022/04) @joscha (2024/10)

Related issues

Fix #21132
Fix #11307

[macjohnny]

thanks for the fix!

[macjohnny]

@tikki100 please update the samples

[tikki100]

@macjohnny I've re-ran on all typescript-fetch samples :) It changed a package.json for some reason as well, so I've added that as a seperate commit, so it can be git reset head^1 if the CI/CD fails again - idk if it's because I'm using the ./run-in-docker.sh script.

Thanks for the swift response! 👍