[Erlang][Client] better code, update sample

[wing328]

• code cleanup
• better code comment
• update samples

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.

cc @tsloughter (2017/11) @jfacorro (2018/10) @robertoaloi (2018/10)

[jfacorro]

I'm probably missing something, but the title says that the code sample is updated in this PR even though I couldn't find that in the diff? Is the code sample updated through the build job?

[wing328]

@jfacorro there's only 1 minor change to the VERSION file: https://github.com/OpenAPITools/openapi-generator/pull/8853/files#diff-286a45eee4f80d6413b2841a22a46bc60b88e156f09cb673d196c2563e1802e4

which is good as the Erlang client generator has been producing the same output despite enhancements in the Default codegen class, etc

[wing328]

@tsloughter thanks for the quick review 👍