This commit also updates Kotlin from beta 2 to RC.

Issue: SPR-15183

Issue: SPR-14954

Issue: SPR-14954

Issue: SPR-14779

Issue: SPR-15196

This commit renames the `RouterFunctions.subroute()` method to `nest()`, to
better represent what it does.

Issue: SPR-14954

Issue: SPR-15196

Fix typo in Javadoc

Added the `pathPrefix` predicate that tests the start of the request
path against a given pattern.

Issue: SPR-14954

Issue: SPR-15259

Rather than returning ExchangeActions that contains ExchangeInfo and
applies a chain of assertions, the exchange operation in WebTestClient
now has an extra step to decode the response.

The outcome of that is ExchangeResult<T>, parameterized with the
decoded body type, and containing the request and response details,
also providing access to built-inassertions via an assertThat()
instance method.

This approach lends itself better to decoding and asserting response
body types with generecis. It is also more friendly to using any
assertion library such as AssertJ since you get the result first
and then deal with assertions.

Issue: SPR-15258

Issue: SPR-14779

Issue: SPR-14670

Issue: SPR-14467

Removed `json()`, `html()` and `xml()` from `RequestPredicates`, since
they were confusingly named and would also require a counterpart that
reads the request `Content-Type` instead of the `Accept` header.

Renamed `RouterFunction.andSame()` to `and()`, and `and()` to
`andOther()`. The reason for this change is that we can expect most
RouterFunctions to be parameterized over ServerResponse, and thus it
makes sense to use the shortest composition method (`and()`) for
composing router functions of the same type.

When a user composes different response types, such as composing a
`RouterFunction<RenderingResponse>` with an
`RouterFunction<EntityResponse<?>`, the `andOther` method is to be used,
but this is a less common scenario.

This commit adds a synchronized block around the PathPatternParser,
since it is not thread-safe.

SPR-15254 RestTemplate with MockMvcClientHttpRequestFactory double encodes URIs

* pr/1327:
  Update copyright header
  Fix typo

Closes gh-1327

See gh-1327

Passing the uri as a string to the MockMvc request builder will cause an encoded uri to become double encoded.

Add assertEntity(Foo.class).map() -> Map<String, Foo>

Add assertBody().map() -> Map<String, String>

Rename andAssert(Consumer<?>) to "consume" in assertion classes

Remove andAssert + andDo from top-level ExchangeActions

Update XmlExpectationsHelper to use an inner class for XML Unit calls
so that the XML Unit dependency remains optional.

Issue: SPR-15156

Issue: SPR-15065

This commit checks that a "Content-Length" request header isn't already
present before adding one in `Netty4ClientHttpRequestFactory`.
`HttpMessageConverter` implementations can write that request header so
the Netty request factory should only write that value when the header
is missing.

If that header is not written (and since we're not dealing with
the HTTP exchange in a chunked-based fashion), the HTTP client might not
send the request body at all.

Issue: SPR-15241

This commit changes the `assertXmlEqual` implementation to compare
expected and actual XML documents without considering the order of XML
nodes.

Issue: SPR-15156

Use new PathPatternParser instead of PathMatcher in
web.reactive.function.server.