MockServerHttpRequest and MockServerHttpResponse now extend the same
abstract base classes that server-specific implementations do and
therefore approximate their behavior more closely.
As an immediate consequence MockServerHttpRequest is read-only after
it is created. Instead it now exposes static builder methods similar
to those found in RequestEntity. This enforces more strictness as well
as recycling of requests in tests and provides nicer builder methods.
To simplify tests DefaultServerWebExchange now offers a constructor
with just a request and response, and automatically creating a
DefaultWebSessionManager.
The spring-test module now also contains client-side reactive mock
request and response implementations. The mock client request extends
the same AbstractClientHttpRequest as client-specific implementations
do. There is no abstract base class for client responses.
Issue: SPR-14590
ba3cc535f1