Auto-configure RSocketRequester.Builder

This commit auto-configures a prototype `RSocketRequester.Builder` bean
for building requester instances. This builder is pre-configured with
auto-detected `RSocketStrategies` (same as the server side).

Closes gh-16280

spring-boot-project/spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -3528,6 +3528,42 @@ about customization possibilities.
 Developers can create `RSocketStrategiesCustomizer` beans to add other strategies,
 assuming there are `Encoder` and `Decoder` implementations available.
 
+[[boot-features-rsocket-requester]]
+=== Calling RSocket Services with `RSocketRequester`
+
+Once the `RSocket` channel is established between server and client, any party can send or
+receive requests to the other.
+
+As a server, you can get injected an `RSocketRequester` instance on any handler method of
+an RSocket `@Controller`. As a client, you need to configure and establish an RSocket
+connection first. Spring Boot auto-configures an `RSocketRequester.Builder` for such cases
+with the expected codecs.
+
+The `RSocketRequester.Builder` instance is a prototype bean, meaning each injection point
+will provide you with a new instance - this is done on purpose since this builder is stateful
+and you shouldn't create requesters with different setups using the same instance.
+
+The following code shows a typical example:
+
+[source,java,indent=0]
+----
+	@Service
+	public class MyService {
+
+		private final RSocketRequester rsocketRequester;
+
+		public MyService(RSocketRequester.Builder rsocketRequesterBuilder) {
+			this.rsocketRequester = rsocketRequesterBuilder
+				.connectTcp("example.org", 9090).block();
+		}
+
+		public Mono<User> someRSocketCall(String name) {
+			return this.requester.route("user").data(payload)
+                   				.retrieveMono(User.class);
+		}
+
+	}
+----
 
 
 [[boot-features-security]]