Jersey body handling is inconsistent with Spring Webflux and Spring MVC

[snicoll]

As discovered by @nosan the Jersey implementation of actuator endpoints accepts complex types in the body whereas Spring Weblux and Spring MVC do not.

An operation is meant to accept a Map<String,String> so the following should fail as it has a nested attribute:

{
  "jobData": {
    "key": "value"
  }
}

To make things consistent, we should update the Jersey implementation so that it fails in a similar fashion.