Upgrade nestjs from 6.0.0 to 9.2.1 (!14534) · Merge requests · OpenAPI Tools / openapi-generator

Created by: sammyquann

Upgrade the nestjs version to align with public-api-service
Header typing in the template didn't align with new versions, so tweaked it to transpile successfully.

I re-generated the jar file and used it to generate the nestjs application code for public-api-service.

Read the contribution guidelines.
[] 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:
```
./mvnw clean package 
./bin/generate-samples.sh
./bin/utils/export_docs_generators.sh
```
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*. For Windows users, please run the script in Git BASH.
File the PR against the correct branch: master (6.3.0) (minor release - breaking changes with fallbacks), 7.0.x (breaking changes without fallbacks)
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