Improve the documentation and discoverability of CoWebFilter

Closes gh-31877

framework-docs/modules/ROOT/pages/languages/kotlin/coroutines.adoc

@@ -14,6 +14,7 @@ Spring Framework provides support for Coroutines on the following scope:
 * Suspending function support in Spring MVC and WebFlux annotated `@Controller`
 * Extensions for WebFlux {spring-framework-api-kdoc}/spring-webflux/org.springframework.web.reactive.function.client/index.html[client] and {spring-framework-api-kdoc}/spring-webflux/org.springframework.web.reactive.function.server/index.html[server] functional API.
 * WebFlux.fn {spring-framework-api-kdoc}/spring-webflux/org.springframework.web.reactive.function.server/co-router.html[coRouter { }] DSL
+* WebFlux {spring-framework-api-kdoc}/spring-web/org.springframework.web.server/-co-web-filter/index.html[`CoWebFilter`]
 * Suspending function and `Flow` support in RSocket `@MessageMapping` annotated methods
 * Extensions for {spring-framework-api-kdoc}/spring-messaging/org.springframework.messaging.rsocket/index.html[`RSocketRequester`]
 

spring-web/src/main/java/org/springframework/web/server/WebFilter.java

@@ -23,6 +23,9 @@
  * be used to implement cross-cutting, application-agnostic requirements such
  * as security, timeouts, and others.
  *
+ * <p>Consider using {@code org.springframework.web.server.CoWebFilter} with
+ * Kotlin Coroutines.
+ *
  * @author Rossen Stoyanchev
  * @since 5.0
  */

spring-web/src/main/kotlin/org/springframework/web/server/CoWebFilter.kt

@@ -26,7 +26,7 @@ import kotlin.coroutines.CoroutineContext
 
 /**
  * Kotlin-specific implementation of the [WebFilter] interface that allows for
- * using coroutines.
+ * using coroutines, including [kotlin.coroutines.CoroutineContext] propagation.
  *
  * @author Arjen Poutsma
  * @author Sebastien Deleuze