Propagate CoroutineContext in CoWebFilter

This provides an elegant and dynamic way to customize the
CoroutineContext in WebFlux with the annotation programming
model.

Closes gh-27522

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

@@ -17,6 +17,8 @@
 package org.springframework.web.server
 
 import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.currentCoroutineContext
 import kotlinx.coroutines.reactor.awaitSingleOrNull
 import kotlinx.coroutines.reactor.mono
 import reactor.core.publisher.Mono
@@ -26,6 +28,7 @@ import reactor.core.publisher.Mono
  * using coroutines.
  *
  * @author Arjen Poutsma
+ * @author Sebastien Deleuze
  * @since 6.0.5
  */
 abstract class CoWebFilter : WebFilter {
@@ -34,6 +37,7 @@ abstract class CoWebFilter : WebFilter {
 		return mono(Dispatchers.Unconfined) {
 			filter(exchange, object : CoWebFilterChain {
 				override suspend fun filter(exchange: ServerWebExchange) {
+					exchange.attributes[COROUTINE_CONTEXT_ATTRIBUTE] = currentCoroutineContext().minusKey(Job.Key)
 					chain.filter(exchange).awaitSingleOrNull()
 				}
 			})}.then()
@@ -47,6 +51,12 @@ abstract class CoWebFilter : WebFilter {
 	 */
 	protected abstract suspend fun filter(exchange: ServerWebExchange, chain: CoWebFilterChain)
 
+	companion object {
+
+		@JvmField
+		val COROUTINE_CONTEXT_ATTRIBUTE = CoWebFilter::class.java.getName() + ".context"
+	}
+
 }
 
 /**