[Java][WebClient] add ResponseEntity return for webclient

[UnleashSpirit]

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.
• File the PR against the correct branch: master, 5.1.x, 6.0.x
• If your PR is targeting a particular programming language, @mention the technical committee members, so they are more likely to review the pull request.

For now we done it by overriding templates but as I have a bit of time and I found that there is already an issue about that, I propose this PR
fix: #5599

For review (java) :
@bbdouglas (2017/07) @sreeshas (2017/08) @jfiala (2017/08) @lukoyanov (2017/09) @cbornet (2017/09) @jeff9finger (2018/01) @karismann (2019/03) @Zomzog (2019/04) @lwlee2608 (2019/10) @nmuesch (2021/01)

[lincetto]

Is it possible to give a boost to this PR? Thanks :)

[UnleashSpirit]

Hi, I rebase my branch with latest master to be up to date but CircleCI failed.
I don't know why, all tests are good in local, any ideas ?

[UnleashSpirit]

Any news about this PR ?
May it be include in 5.2.2 milestone (like PR #9329)

[UnleashSpirit]

Here a new proposal with merged function to avoid duplicated code

[wing328]

LGTM