WebTestClient now defines all the steps from setup to performing
an exchange and applying expectations.
The order of expectations now ensures the response status and headers
are verified first since that's available before the body is consumed
and also because it determines how the body is to be decoded, i.e.
error vs success scenarios.
There is now a built-in option for verifying the response as a Map
along with Map-specific assertions.
There are similar options for verifying the response as a List as well
as whether to "collect" the list or "take" the first N elements from
the response stream.