Bastien Jansen

Upgrade to Spring Boot 4.0 / Spring 7

1

`OkHttp3ClientHttpRequestFactory` has been [deprecated](https://github.com/spring-projects/spring-framework/commit/efb6abc43f550c2be20f39ad9ce65346ee5ebd65) in Spring 6 and then removed in Spring 7, so I had to improvise and decided to switch to Apache HttpClient 5.