Issue: SPR-13019
(cherry picked from commit 02d28ae9)

Issue: SPR-12956

Prior to this commit, the `client-library-url` XML attribute was not
effective in the MVC namespace, leaving the default value configured:

```xml
<websocket:sockjs client-library-url="/js/sockjs.js" />
```

This commit fixes the sockjs namespace handler and makes sure that this
attribute is configured on the `SockJsService` Bean to be created.

Issue: SPR-12874

(cherry picked from commit d23893fd)

(cherry picked from commit 2b340946)

Issue: SPR-12728

Issue: SPR-12727

This commit adds support for a same origin check that compares
Origin header to Host header. It also changes the default setting
from all origins allowed to only same origin allowed.

Issues: SPR-12697, SPR-12685
(cherry picked from commit 6062e155)

This commit introduces the following changes:
 - Requests without Origin header are not rejected anymore
 - Disable Iframe when allowedOrigins is not empty and not equals to *
 - The Iframe is not cached anymore in order to have a reliable origin check
 - allowedOrigins must not be null or empty
 - allowedOrigins format is now validated (should be * or start by http(s)://)

Issue: SPR-12660
(cherry picked from commit 9b3319b3)

Before this change the WebSocketTransportHandler passed
Collections.emptyMap as attributes to the HandshakeHandler because
it didn't matter what attributes the underlying WebSocketSession has
since it is wrapped by the SockJsSession and that's what exposed for
use everywhere.

This change has the WebSocketTransportHandler passing the attributes
from the SockJsSession instead since it's more accurate for the
underlying WebSocketSession to have access to the same map instance
and it allows the HandshakeHandler to change the attributes even if
it doesn't need to do that today.

Issue: SPR-12716

Issue: SPR-12658

The following two refinements have been added:
1) SockJS doesn't support binary messages so don't even try
2) don't bother if payload.length == 0

Issue: SPR-12475

After this change the StompSubProtocolHandler sends STOMP frames
with content-type=octet-stream as a binary WebSocket message.

Issue: SPR-12475

Issue: SPR-12516

This commit introduces the SpringHandlerInstantiator
class, a Jackson HandlerInstantiator that allows to autowire
Jackson handlers (JsonSerializer, JsonDeserializer, KeyDeserializer,
TypeResolverBuilder and TypeIdResolver) if needed.

SpringHandlerInstantiator is automatically used with
@EnableWebMvc and <mvc:annotation-driven />.

Issue: SPR-10768

With this commit, Jackson builder is now used in spring-websocket
to create the ObjectMapper instance.

It is not possible to use the builder for spring-messaging
and spring-jms since these modules don't have a dependency on
spring-web, thus they now just customize the same features:
 - MapperFeature#DEFAULT_VIEW_INCLUSION is disabled
 - DeserializationFeature#FAIL_ON_UNKNOWN_PROPERTIES is disabled

Issue: SPR-12293

Issue: SPR-12497

(cherry picked from commit 7e07f3d0)

Upgrade undertow dependency to 1.1.0.Final.
Add support for undertow 1.1.0.Final in the
UndertowRequestUpgradeStrategy, after a breaking change in the
`io.undertow.websockets.jsr.ConfiguredServerEndpoint` constructor.

Issue: SPR-12302

Prior to this change, duplicate SubProtocolHandlers could be registered
when configuring STOMP with several registrations:

    public void registerStompEndpoints
          (final StompEndpointRegistry registry) {
      this.endpointRegistry.addEndpoint("/stompOverWebSocket");
      this.endpointRegistry.addEndpoint("/stompOverSockJS").withSockJS();
    }

This commit registers sub-protocols in a Set instead of a list (see
SubProtocolWebSocketHandler), thus fixing the issue.

Issue: SPR-12403

Issue: SPR-12379

Issues: SPR-12283

This commit introduces a new OriginHandshakeInterceptor. It filters
Origin header value against a list of allowed origins.

AbstractSockJsService as been modified to:
 - Reject CORS requests with forbidden origins
 - Disable transport types that does not support CORS when an origin
   check is required
 - Use the Origin request header value instead of "*" for
   Access-Control-Allow-Origin response header value
   (mandatory when  Access-Control-Allow-Credentials=true)
 - Return CORS header only if the request contains an Origin header

It is possible to configure easily this behavior thanks to JavaConfig API
WebSocketHandlerRegistration#addAllowedOrigins(String...) and
StompWebSocketEndpointRegistration#addAllowedOrigins(String...).
It is also possible to configure it using the websocket XML namespace.

Please notice that this commit does not change the default behavior:
cross origin requests are still enabled by default.

Issues: SPR-12226

Before this change the simple broker simply removed subscriptions
upon receiving a DISCONNECT message assuming it was a result of
a client STOMP WebSocket session ending.

However, if the server-side application sends a DISCONNECT to
the broker in order to terminate a session, the STOMP WebSocket
session could remain unware without any further action. This
change ensures the simple broker sends a DISCONNECT_ACK message
downstream whenever it receives a DISCONNECT.

Issue: SPR-12288

This change adds a ChannelInterceptor that flips the immutable flag on
messages being sent. This allows components sending messages to leave
the message mutable for interceptors to further apply modifications
before the message is sent (and exposed to concurrency).

The interceptor is automatically added with the STOMP/WebSocket Java
and XML config and the StompSubProtocolHandler leaves parsed incoming
messages mutable so they can be further modified before being sent.

Issue: SPR-12321

Issue: SPR-12352

Issue: SPR-12340

Use explicit flag whether to copy all attributes.