https://www.baeldung.com/rest-with-spring-series

2025
https://habr.com/ru/companies/maxilect/articles/896240/
    ! speed up
    https://github.com/burov4j/spring-undertow-example
2023
https://sudarshandoiphode.hashnode.dev/understanding-the-power-of-responseentityt-in-spring-framework