In the generated java code, it is usefull to have the generated java api
use the @deprecated annotation. This enable to leverage this annotation
at runtime to trigger specific logging for instance.

In the generated interface, use the @deprecated annotation.
Also, in the jax-rs implementation that links the jax-rs api with the
cdi bean implementing the interface, use the
@SuppressWarnings("deprecation") annotation. This way the deprecation
warning is not shown in generated code.

One can use the interface as before: the java compiler can then tell
which implementations do implement a deprecated api, using a warning.
If the implementation itself also sets the @deprecated annotation, then
there is no warning, unless the implementation is called at another
place in the code.

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 (5.3.0), 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.

cc @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)