[Java][Spring] Change methodBody.mustache for webflux bean validation

Created by: gimbimloki

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.
• 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.
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Technical Committee

@cachescrubber (2022/02) @welshm (2022/02) @MelleD (2022/02) @atextor (2022/02) @manedev79 (2022/02) @javisst (2022/02) @borsch (2022/02) @banlevente (2022/02) @Zomzog (2022/09)

PR Description

Change JavaSpring/bodyMethod.mustache for webflux bean validation. Request body object is not validated in API interface that is generated by generator. Because 'bodyParam' Mono/Flux is not called in API Interface, Bean Validation is not working on 'bodyParam'.

Example

    default Mono<ResponseEntity<Void>> testBodyWithQueryParams(String query,
        @Valid Mono<User> body, // Use Bean Validation
        ServerWebExchange exchange) {
        Mono<Void> result = Mono.empty();
        exchange.getResponse().setStatusCode(HttpStatus.NOT_IMPLEMENTED);
        return result.then(Mono.empty()); // 'body' is not called and validated.
    }