When describing an operation that returns an array of strings, the openapi-generator for java-webclient generates an API returning the array of strings in a single string.

Recommended solution by Spring developers (see spring-projects/spring-framework#22662 and https://docs.spring.io/spring/docs/current/spring-framework-reference/web-reactive.html#webflux-codecs-jackson) is to use a Mono for string arrays.

The PR contains the change that will generate the API client of the operation that returns an array of strings to Mono<List> instead of Flux.

Close: #7118

PR checklist

• 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.
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  ./mvnw clean package 
  ./bin/generate-samples.sh
  ./bin/utils/export_docs_generators.sh
  

  Commit all changed files.
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