Add example for Immutables+MapStruct

Would be nice to have an example that shows the usage of MapStruct with Immutables.

I was trying to use MapStruct with Immutables and couldn't find a comprehensive example or guide that could walk users through this set up. Would be nice to have this example.

I created a sample Spring REST service that uses MapStruct and Immutables to post my question on StackOverflow.

If you think this is a good addition, with some help and guidance I am willing to improve this to have it included as an example.

未指定任何 repository 檔案或測試。先檢視 mapstruct-examples 中現有的範例和連結的示範 Spring REST 服務，然後將其 MapStruct 和 Immutables 設定與專案慣例進行比較。新增一個展示此整合的完整範例或指南後，即視為完成。