feat: add support for minimal-update option in maven plugin

[julius-d]

--minimal-update is an existing parameter of the OpenAPI Generator CLI tool.
This PR adds support for the minimalUpdate parameter to the OpenAPI Generator Maven plugin,
bringing feature parity with the CLI tool.

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 || exit
  ./bin/generate-samples.sh ./bin/configs/*.yaml || exit
  ./bin/utils/export_docs_generators.sh || exit
  

  (For Windows users, please run the script in WSL)
  Commit all changed files.
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