springboot Fix deprecation warnings caused by BodyInserters.fromObject

Hi,

this PR fixes a couple of deprecation warnings caused by BodyInserters.fromObject which is replaced by ´BodyInserters.fromValue`.

Cheers, Christoph

Comment From: dreis2211

Test failure is related to checkstyle issues. See #18351

Comment From: wilkinsona

Thanks again, @dreis2211!

Comment From: jortiz425

Hi, Another solution could be overriden by the Body.Inserters.fromValue method.