Configure RSocket server support in GraphQL

This commit adds the RSocket server auto-configuration for GraphQL.

See gh-30453

spring-boot-project/spring-boot-docs/src/docs/asciidoc/web/spring-graphql.adoc

@@ -1,7 +1,7 @@
 [[web.graphql]]
-== Spring GraphQL
-If you want to build GraphQL applications, you can take advantage of Spring Boot's auto-configuration for {spring-graphql}[Spring GraphQL].
-The Spring GraphQL project is based on https://github.com/graphql-java/graphql-java[GraphQL Java].
+== Spring for GraphQL
+If you want to build GraphQL applications, you can take advantage of Spring Boot's auto-configuration for {spring-graphql}[Spring for GraphQL].
+The Spring for GraphQL project is based on https://github.com/graphql-java/graphql-java[GraphQL Java].
 You'll need the `spring-boot-starter-graphql` starter at a minimum.
 Because GraphQL is transport-agnostic, you'll also need to have one or more additional starters in your application to expose your GraphQL API over the web:
 
@@ -22,6 +22,9 @@ Because GraphQL is transport-agnostic, you'll also need to have one or more addi
 | HTTP, WebSocket
 | Spring WebFlux
 
+| `spring-boot-starter-rsocket`
+| TCP, WebSocket
+| Spring WebFlux on Reactor Netty
 |===
 
 
@@ -74,9 +77,11 @@ Spring Data repositories annotated with `@GraphQlRepository` and extending one o
 are detected by Spring Boot and considered as candidates for `DataFetcher` for matching top-level queries.
 
 
+[[web.graphql.transports]]
+=== Transports
 
-[[web.graphql.web-endpoints]]
-=== Web Endpoints
+[[web.graphql.transports.http-websocket]]
+==== HTTP and WebSocket
 
 The GraphQL HTTP endpoint is at HTTP POST "/graphql" by default. The path can be customized with configprop:spring.graphql.path[].
 
@@ -91,10 +96,6 @@ This is quite useful for retrieving information from an HTTP request header and
 With Spring Boot, you can declare a `WebInterceptor` bean to have it registered with the web transport.
 
 
-
-[[web.graphql.cors]]
-=== CORS
-
 {spring-framework-docs}/web.html#mvc-cors[Spring MVC] and {spring-framework-docs}/web-reactive.html#webflux-cors[Spring WebFlux] support CORS (Cross-Origin Resource Sharing) requests.
 CORS is a critical part of the web config for GraphQL applications that are accessed from browsers using different domains.
 
@@ -111,6 +112,19 @@ Spring Boot supports many configuration properties under the `spring.graphql.cor
 ----
 
 
+[[web.graphql.transports.rsocket]]
+==== RSocket
+
+RSocket is also supported as a transport, on top of WebSocket or TCP.
+Once the <<messaging#messaging.rsocket.server-auto-configuration,RSocket server is configured>>, we can configure our GraphQL handler on a particular route using configprop:spring.graphql.rsocket.mapping[].
+For example, configuring that mapping as `"graphql"` means we can use the `RSocketGraphQlClient` as follows.
+
+For RSocket over TCP:
+include::code:RSocketGraphQlClientExample[tag=tcp]
+
+For RSocket over WebSocket:
+include::code:RSocketGraphQlClientExample[tag=websocket]
+
 
 [[web.graphql.exception-handling]]
 === Exceptions Handling
@@ -126,7 +140,7 @@ Spring Boot will automatically detect `DataFetcherExceptionResolver` beans and r
 
 Spring GraphQL offers infrastructure for helping developers when consuming or developing a GraphQL API.
 
-Spring GraphQL ships with a default https://github.com/graphql/graphiql[GraphiQL] page that is exposed at "/graphiql" by default.
+Spring GraphQL ships with a default https://github.com/graphql/graphiql[GraphiQL] page that is exposed at `"/graphiql"` by default.
 This page is disabled by default and can be turned on with the configprop:spring.graphql.graphiql.enabled[] property.
 Many applications exposing such a page will prefer a custom build.
 A default implementation is very useful during development, this is why it is exposed automatically with <<using#using.devtools,`spring-boot-devtools`>> during development.